Rozprawy doktorskie: „Quantum condensed matter”

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Zonzo, Giuseppe. "Quantum Information Theory in Condensed Matter Physics". Doctoral thesis, Universita degli studi di Salerno, 2017. http://hdl.handle.net/10556/2625.

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2015 - 2016
Inthe“standard”Gizburg-Landauapproach,aphasetransitionisintimately connected to a local order parameter, that spontaneously breaks some symmetries. In addition to the “traditional” symmetry-breaking ordered phases, a complex quantum system exhibits exotic phases, without classical counterpart, that can be described, for example, by introducing non-local order parameters that preserve symmetries. In this scenario, this thesis aims to shed light on open problems, such as the localdistinguishabilitybetweengroundstatesofasymmetry-breakingordered phase and the classiﬁcation of one dimensional quantum orders, in terms of entanglement measures, in systems for which the Gizburg-Landau approach fails. In particular, I brieﬂy introduce the basic tools that allow to understand the nature of entangled states and to quantify non-classical correlations. Therefore, I analyze the conjecture for which the maximally symmetry-breaking ground states (MSBGSs) are the most classical ones, and thus the only ones selected in real-world situations, among all the ground states of a symmetry-breaking ordered phase. I make the conjecture quantitatively precise, by proving that the MSBGSs are the only ones that: i) minimize pairwise quantum correlations, as measured by the quantum discord; ii) are always local convertible, by only applying LOCC transformations; iii) minimize the residual tangle, satisfying at its minimum the monogamy of entanglement. Moreover,Ianalyzehowevolvesthedistinguishability,afterasuddenchange of the Hamiltonian parameters. I introduce a quantitative measure of distinguishability, in terms of the trace distance between two reduced density matrices. Therefore, in the framework of two integrable models that falls in two different classes of symmetries, i.e. XY models in a transverse magnetic ﬁeld and the N-cluster Ising models, I prove that the maximum of the distinguishability shows a time-exponential decay. Hence, in the limit of diverging time, all the informations about the particular initial ground state disappear, even if a system is integrable. Far away from the Gizburg-Landau scenario, I analyze a family of fullyanalyticalsolvableonedimensionalspin-1/2models,namedtheN-clustermodels in a transverse magnetic ﬁeld. Regardless of the cluster size N + 2, these modelsexhibitaquantumphasetransition,thatseparatesaparamagneticphase from a cluster one. The cluster phase coresponds to a nematic ordered phase or a symmetry-protected topological ordered one, for even or odd N respectively. Using the Jordan-Wigner transformations, it is possible to diagonalize these models and derive all their spin correlation functions, with which reconstruct their entanglement properties. In particular, I prove that these models have only a non-vanishing bipartite entanglement, as measured by the concurrence, between spins at the endpoints of the cluster, for a magnetic ﬁeld strong enough. Moreover, I introduce the minimal set of nonlinear ground-states functionals to detect all 1-D quantum orders for systems of spin-1/2 and fermions. I show that the von Neumann entanglement entropy distinguishes a critical systemfromanoncriticalone,becauseofthelogarithmicdivergenceataquantum critical point. The Schmidt gap detect the disorder of a system , because it saturates to a constant value in a paramagnetic phase and goes to zero otherwise. The mutual information, between two subsystems macroscopically separated, identiﬁesthesymmetry-breakingorderedphases,becauseofitsdependenceon the order parameters. The topological order phases, instead, via their deeply non-locality, can be characterized by analyzing all three functionals. [edited by author]
In aggiunta alle tradizionali fasi ordinate con rottura spontanea di simmetria, ben descritte con un approccio alla Gizburg-Landau, dove una transizione di fase `e intimamente connessa alla rottura spontanea di qualche simmetria e ad un parametro d’ordine locale, un sistema quantistico presenta anche fasi esotiche,senzaanalogoclassico,chesonoperesempiocaratterizzatedaparametri d’ordine non locali, senza una necessaria rottura di simmetria. Partendo da questi presupposti, questa tesi si pone come obiettivo quello di fare luce su alcuni problemi ancora aperti, come la distinguibilit`a tra stati fondamentaliinsistemiquantisticiconrotturaspontaneadisimmetriaelaclassiﬁcazionedituttelefasipresentiinsistemiunidimensionalidispin-1/2efermioni, per i quali l’approccio alla Gizburg-Landau non fornisce una descrizione adeguata. Inparticolare,sid`aunaspiegazioneall’ipotesisecondolaqualeglistatifondamentali che rompono massimamente la simmetria sono quelli pi`u classici, e quindi selezionati dalla decoerenza dell’ambiente, tra tutti gli stati fondamentali,edenergeticamenteequivalenti,diunafaseordinataconrotturaspontanea di simmetria. Si dimostra, infatti, che gli stati che rompono massimamente la simmetria sono gli unici stati che soddisfano tre criteri di classicalit`a: i) minimizzano l’entanglement bipartito, come quantiﬁcato dalla discord; ii) sono gli uniciversocuituttiglialtristatifondamentalisonolocalmenteconvertibili,mediante LOCC; iii) minimizzano il tangle residuo, soddisfacendo al minimo la monogamia dell’entanglement. Viene analizzato, inoltre, come evolve la distinguibilit`a tra stati fondamentali, dopo un quench dei parametri Hamiltoniani. Dopo aver introdotto una misura quantitativa della distinguibilit`a, in termini della distanza tra due matrici densit`a ridotte, si dimostra, per due sistemi integrabili con diverse classi di simmetria, nel dettaglio il modello XY in campo magnetico e i modelli NclusterIsing,cheladistinguibilit`adecadeesponenzialmenteneltempoequindi, nel limite di tempi lunghi, tutte le informazioni sullo stato fondamentale di partenza si perdono, anche per sistemi integrabili, nei quali la termalizzazione non si veriﬁca. LontanodalloscenarioGizburg-Landau,sianalizzaunafamigliadimodelli di spin-1/2 esattamente risolvibili, nel dettaglio i modelli N-cluster in campo magnetico, che mostrano una transizione tra una fase disordinata e una di tipo cluster, che pu`o essere nematica o topologica, rispettivamente per N pari o dispari. Usando le trasformazioni di Jordan-Wigner `e possibile diagonalizzare questi modelli, ricavare lo stato fondamentale, le funzioni di correlazione fermioniche e tutte le loro propriet`a di entanglement di. Si dimostra che questi modellinonhannoentanglementmultipartito,masoloentanglementbipartito, come misurato dalla concurrence, tra due spin alle estremit`a del cluster, per un campo magnetico sufﬁcientemente intenso. Inoltre, sidimostrachel’entropiadivonNeumann,loSchmidtgapelamutualinformationrappresentanoilsetminimodifunzionalinonlinearidellamatrice densit`a ridotta, mediante le quali caratterizzare tutte le fasi presenti in sistemi unidimensionali di spin -1/2 e fermioni. In particolare, l’entropia di von Neumann caratterizza la criticalit`a del sistema, per la sua divergenza logaritmica al punto critico; lo Schmidt gap caratterizza il disordine di un sistema, perch´e satura ad un valore costante nelle fasi disordinate e va rapidamente a zero altrove; la mutual information cattura le fasi ordinate con rottura spontanea di simmetria, per le quali cio` e `e possibile deﬁnire un parametro d’ordine diverso da zero su un supporto ﬁnito. Le fasi topologiche, per via della loro natura fortemente non locale, necessitano di tutte e tre i funzionali per essere individuate. [a cura dell'autore]
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2

Gauger, E. M. "Applications of quantum coherence in condensed matter nanostructures". Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:fb792980-bfc4-4771-b5d5-b9ecc7d40cd8.

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This thesis is concerned with studying the fascinating quantum properties of real-world nanostructures embedded in a noisy condensed matter environment. The interaction with light is used for controlling and manipulating the quantum state of the systems considered here. In some instances, laser pulses also provide a way of actively probing and controlling environmental interactions. The first two research chapters assess two different ways of performing all-optical spin qubit gates in self-assembled quantum dots. The principal conclusion is that an `adiabatic' control technique holds the promise of achieving a high fidelity when all primary sources of decoherence are taken into account. In the next chapter, it is shown that an optically driven quantum dot exciton interacting with the phonons of the surrounding lattice acts as a heat pump. Further, a model is developed which predicts the temperature-dependent damping of Rabi oscillations caused by bulk phonons, finding an excellent agreement with experimental data. A different system is studied in the following chapter: two electron spin qubits with no direct interaction, yet both exchange-coupled to an optically active mediator spin. The results of this study show that these general assumptions are sufficient for generating controlled electron spin entanglement over a wide range of parameters, even in the presence of noise. Finally, the Radical Pair model of the avian compass is investigated in the light of recent experimental results, leading to the surprising prediction that the electron spin coherence time in this molecular system seems to approach the millisecond timescale.

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Baggioli, Matteo. "Gravity, holography and applications to condensed matter". Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/395205.

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Los sistemas fisicos fuertemente acoplados, junto a sus correspondientes y por lo general exoticas caracteristicas, son imposibles de tratar mediante los enfoques perturbativos convencionales que en estos casos no son capaces de proporcionar una herramienta controlable y robusta. Sin embargo, los efectos no perturbativos y fenomenos fuertemente correlacionados abundan en la fisica, especialmente en la Fisica de la Materia Condensada. La correspondencia AdS / CFT, que nace de el estimulo de las ideas y esfuerzos empleados en descubrir una posible descripcion de la gravedad cuantica, proporciona una perspectiva inesperada e innovadora para hacer frente a las teor√≠as de campo fuertemente acopladas. En su formulacion mas general este planteamiento ofrece un arma efectiva para hacer frente a ese tipo de problemas utilizando una descripcion dual de teorias gauge mediante teorias de gravedad que resulta ser mas simple que la original. En los ultimos anos ha habido un gran numero de avances aplicando esta dualidad a temas modernos e innovadores en materia condensada, tales como la naturaleza de los metales raros o el mecanismo que subyace la superconductividad de alta Tc. La relajacion del momento es un ingrediente omnipresente e inevitable de cualquier sistema realista en Materia Condensada. En los materiales del mundo real la presencia de un reticulo, de impurezas, o de desorden hacen que el momento se disipe, y se da lugar a efectos fisicos relevantes, tales como las propiedades de transporte de corriente continua sean finitas,es decir, la conductividad. Hay varias preguntas abiertas relacionadas a dichas cantidades, especialmente en el limite de maxima relajacion donde surgen nuevos estados aislantes y transiciones de fase cuantica inesperadas entre los estados ultimos y metalicos (MIT) . El objetivo principal de esta tesis es la introduccion de disipacion de momento y sus efectos en el contexto Ads/CMT, es decir, las aplicaciones de la dualidad Gauge-Gravedad en materia condensada. Una manera conveniente y efectiva de romper la simetria traslacional de la teoria cuantica de campos dual es proporcionada por las teorias de gravedad masiva (GM), que constituye una herramienta facil y manejable para atacar varias e interesantes preguntas sobre sistemas fuertemente acoplados con disipacion de impulso. Originalmente concebido para resolver problemas en cosmologia, la GM puede ahora ser empleada bajo una perspectiva completamente nueva y podria convertirse en una herramienta √∫til para aplicaciones del ''mundo real'' y ''de bajas energias''. Consideramos modelos genericos de gravedad masiva en espacio-tiempos asint√≥ticamente anti de Sitter y los analizamos usando tecnicas holograficas.
Strongly coupled physical systems along with their corresponding, and usually exotic, features are elusive and not suitable to be described by conventional and perturbative approaches, which in those cases are not able to provide a controllable and robust tool for computations. Nevertheless non perturbative effects and strongly correlated frameworks are ubiquitous in nature, expecially in Condensed Matter physics. The AdS/CFT correspondence, born from the excitement of ideas and efforts employed in finding out a possible description of Quantum Gravity, lead to a flurry of fresh air into the subject, introducing an unexpected and brandnew perspective for dealing with strongly coupled field theories. In its more general formulation, known as Gauge-Gravity duality, this setup accounts for an effective and efficient weapon to tackle those kind of problems using a dual gravitational description which turns out to be way easier than the original one. In the last years, a huge number of developments have been achieved in applying the duality towards modern and hot condensed matter misteries, such as the Strange Metals nature or the mechanism underlying the High-Tc Superconductivity.\\ Momentum relaxation is an ever-present and unavoidable ingredient of any realistic Condensed Matter system. In real-world materials the presence of a lattice, impurities or disorder forces momentum to dissipate and leads to relevant physical effects such as the finiteness of the DC transport properties, i.e. conductivities. Several open questions are connected to those quantities expecially in the limit of strong momentum relaxation where novel insulating states appear and unexpected quantum phase transitions between the latter and metallic states (MIT) arise.\\[0.2cm] The main purpose of this thesis is the introduction of momentum dissipation and its consequent effects into the framework of AdS/CMT, namely the applications of the Gauge-Gravity duality to Condensed Matter. \\ A convenient and effective way of breaking translational symmetry of the the dual quantum field theory is provided by Massive Gravity (MG) theories, which constitues a tractable and easy tool to adress several interesting questions in strongly coupled systems with momentum dissipation. Born to solve cosmological puzzles, MG can now be reconsidered under a completely new perspective and could become a useful framework for ''Real-world" phenomena and "low energy" applications. We consider generic massive gravity models embedded into asymptotically Anti de Sitter spacetime and we analyze them using holographic techniques.

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Babadi, Mehrtash. "Non-equilibrium dynamics of artificial quantum matter". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11114.

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The rapid progress of the field of ultracold atoms during the past two decades has set new milestones in our control over matter. By cooling dilute atomic gases and molecules to nano-Kelvin temperatures, novel quantum mechanical states of matter can be realized and studied on a table-top experimental setup while bulk matter can be tailored to faithfully simulate abstract theoretical models. Two of such models which have witnessed significant experimental and theoretical attention are (1) the two-component Fermi gas with resonant $s$-wave interactions, and (2) the single-component Fermi gas with dipole-dipole interactions. This thesis is devoted to studying the non-equilibrium collective dynamics of these systems using the general framework of quantum kinetic theory.
Physics

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Liu, Wensheng. "Applications of effective field theory to condensed matter /". Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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Korkusinski, Marek. "Correlations in semiconductor quantum dots". Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/29128.

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In this Thesis, I present a theoretical study of correlation effects in strongly interacting electronic and electron-hole systems confined in semiconductor quantum dots. I focus on three systems: N electrons in a two-dimensional parabolic confinement in the absence and in the presence of a magnetic field, an electron-hole pair confined in a vertically coupled double-quantum-dot molecule, and a charged exciton in a quantum-ring confinement in a magnetic field. To analyse these systems I use the exact diagonalisation technique in the effective-mass approximation. This approach consists of three steps: construction of a basis set of particle configurations, writing the Hamiltonian in this basis in a matrix form, and numerical diagonalisation of this matrix. Each of these steps is described in detail in the text. Using the exact diagonalisation technique I identify the properties of the systems due to correlations and formulate predictions of how these properties could be observed experimentally. I confront these predictions with results of recent photoluminescence and transport measurements. First I treat the system of N electrons in a parabolic confinement in the absence of magnetic field and demonstrate how its properties, such as magnetic moments, can be engineered as a function of the system parameters and the size of the Hilbert space. Next I analyse the evolution of the ground state of this system as a function of the magnetic field. In the phase diagram of the system I identify the spin-singlet nu = 2 phase and discuss how correlations influence its phase boundaries both as a function of the magnetic field and the number of electrons. I also demonstrate that in higher magnetic fields electronic correlations lead to the appearance of spin-depolarised phases, whose stability regions separate the weakly correlated phases with higher spin. Further on, I consider electron-hole systems. I show that the Coulomb interaction leads to entanglement of the states of an electron and a hole confined in a pair of vertically coupled quantum dots. Finally I consider the system of two electrons and one hole (a negatively charged exciton) confined in a quantum ring and in the presence of the magnetic field. I show that the energy of a single electron in the ring geometry exhibits the Aharonov-Bohm oscillations as a function of the magnetic field. In the case of the negatively charged exciton these oscillations are nearly absent due to correlations among particles, and as a result the photoluminescence spectra of the charged complex are dominated by the energy of the final-state electron. The Aharonov-Bohm oscillations of the energy of a single electron are thus observed directly in the optical spectra.

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Gibb, Kevin. "The quantum confined Stark effect and Wannier Stark ladders in InxGa1-xAs quantum wells and superlattices". Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7704.

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The effects of an applied bias in the longitudinal or growth direction on four In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As-GaAs strained single quantum wells and three strained layer superlattices have been studied using photocurrent and electroreflectance spectroscopy at liquid helium temperature. Weak applied electric fields on the quantum well samples gives rise to a red quadratic shift to the lowest interband transition between the first confined electron (E1) and heavy-hole (H1) levels, the quantum confined Stark effect (QCSE). The magnitude of the QCSE increases with well width. This field dependence becomes subquadratic at high applied fields due to carrier accumulation on the low energy side of the wells. Superlattices with relatively small periods, i.e. 10 nm, exhibit interwell coupling giving rise to a miniband structure under flatband conditions. The application of an electric field removes the interwell coupling giving rise to a ladder like progression in energy for the interband transition energies, called Wannier Stark ladders. The measured exciton transition energies follow a linear field dependence given by the product of the Stark ladder index, the superlattice period, and the electric field. The low field behaviour is more complex due to the Coulomb interaction between the electrons and heavy-holes. The measured field dependent exciton transition energies for the quantum wells agree well with single particle model calculations, while for the superlattice samples the exciton Stark ladder calculations of Dignam and Sipe have yielded good agreement with the measured data.

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Morris, Richard. "Studies towards quantum magnonics". Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:89784b64-de31-457f-b9b2-54125c862632.

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This thesis reports on recent results which pave the way for future experiments in the emerging field of quantum magnonics. Chapter 1 presents a brief outline of the field of magnonics, which provides the context in which quantum magnonics has begun to develop. Chapter 2 provides an introduction to the theory of spin waves, which is necessary to understand the experiments reported in the thesis. In Chapter 3, the experimental methods and materials used to carry out the investigations in the thesis are described. Chapter 4 describes the coupling of resonant magnon modes in a sphere of yttrium-iron garnet to photon modes in a coplanar-waveguide resonator. Strong coupling is achieved to multiple magnon modes, and a theoretical model is used to identify the magnon modes which couple most strongly to the photon mode. In Chapter 5, the behaviour of propagating magnon modes is investigated in a waveguide formed from a thin film of yttrium-iron garnet. Two different configurations are investigated supporting different types of propagating mode, namely backward-volume and surface spin waves. Simulations are performed which reproduce the main features of the data. Chapter 6 characterises the effect of the gadolinium-gallium garnet substrate on propagating spin waves. The magnitude of this effect is dependent on both the orientation and temperature of the sample. Finally, Chapter 7 provides a short summary of the results of the thesis, and speculates on how they may inform future work in the field.

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Eastmond, John F. G. "Numerical studies of two problems in condensed matter physics : quantum transport and quantum antiferromagnets". Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315716.

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Fidkowski, Lukasz. "Singularity resolution in string theory and new quantum condensed matter phases /". May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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Rost, A. W. "Magnetothermal properties near quantum criticality in the itinerant metamagnet Sr₃Ru₂O₇ /". St Andrews, 2009. http://hdl.handle.net/10023/837.

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Maciejko, Joseph. "Time-dependent quantum transport in mesoscopic structures". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99346.

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In this thesis, we present a theory to calculate the time-dependent current flowing through an arbitrary noninteracting nanoscale phase-coherent device connected to arbitrary noninteracting external leads, in response to sharp step- and square-shaped voltage pulses. Our analysis is based on the Keldysh nonequilibrium Green's functions formalism, and provides an exact analytical solution to the transport equations in the far from equilibrium, nonlinear response regime. The essential feature of our solution is that it does not rely on the commonly used wideband approximation where the coupling between device scattering region and leads is taken to be independent of energy, and as such provides a way to perform transient transport calculations from first principles on realistic systems, taking into account the detailed electronic structure of the device scattering region and the leads. As an illustration of the general theory, we perform a toy model calculation for a quantum dot with Lorentzian linewidth and show how interesting finite-bandwidth effects arise in the time-dependent current dynamics. Finally, we describe possible generalizations of our theory to the cases of superconducting leads (an example of broken symmetry) and one-dimensional leads in the Luttinger liquid regime (an example of an interacting system).

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Wei, Haiqing 1970. "Coherent AC transport theory and quantum capacitance". Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20979.

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The AC phase-coherent transport in mesoscopic structures is studied via a scattering approach. A general theory is presented under the guidance of two physical principles: charge and current conservation, gauge invariance. As the AC response is intrinsically a many-body problem, we have to treat the scattering problem and the charge redistribution effects in a self-consistent manner.
One quantity of particular interest is the mesoscopic capacitance. In mesoscopic structures where the electric screening length is comparable to the geometric size, the experimentally relevant capacitance is no longer due to geometry alone but to the electro-chemical potential and the capacitance crucially depends on the density of states of the conductor. Furthermore, the phase-coherent nature of the carrier motion leads to striking asymmetric effects in the magneto-capacitance. The general theory is put forth into numerical simulations where the theory is justified.
The study of AC transport in mesoscopic structures should not only help us to better understand the physics of many-body systems, but should also provide valuable knowledge in characterizing and controlling small electronic devices which is of great technological importance.

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Young, Carolyn 1979. "Many-body cotunneling in coupled quantum dots". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101692.

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The zero-temperature equilibrium conductance of mesoscopic devices due to single-particle resonant tunneling was first described by Landauer [1]. The Landauer formula was later extended to the multi-channel case by Fisher and Lee [2], who reduced the problem of calculating electronic transport properties to the problem of solving for the Green's function for a given system geometry.
In this work, the single-particle formalism is extended to the study of higher-order two-particle cotunneling processes by considering many-body Green's functions. The effect of attaching leads to the system is described in terms of a two-particle self-energy, whose analytical form is written in terms of a Feynman path integral over all possible tunneling processes between the leads and the device. In addition, an efficient numerical technique for the calculation of the fully dressed Green's function of a device region attached to two-particle leads is presented.
The problem of two-particle transport is then approached, and an analogy to single-particle transport on the infinite plane is drawn. It is shown that, for nonspin flip cotunneling processes, the two-particle transport result can be related to the single-particle conductance by way of a simple convolution. Finally, results for the cotunneling contribution to the conductance of double quantum dots, or charge qubits, are presented.

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Li, Zhou. "Multi-channel quantum dragons in rectangular nanotubes". Thesis, Mississippi State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1586984.

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Recently the theoretical discovery of single channel quantum dragons has been reported. Quantum dragons are a class of nanodevices that may have strong disorder but still permit energy-independent total quantum transmission of electrons. This thesis illustrates that multi-channel quantum dragons also exit in rectangular nanotubes and provide an approach to construct multi-channel quantum dragons in rectangular nanotubes. Rectangular nanotube multi-channel quantum dragons have been validated by matrix method based quantum transmission calculation. This work could pave the way for constructing multi-channel quantum dragons from more complex nanostructures such as single-walled zigzag carbon nanotubes and single-walled armchair carbon nanotubes.

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Higginbotham, Andrew Patrick. "Quantum Dots for Conventional and Topological Qubits". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:23845477.

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This thesis presents a series of quantum dot studies, performed with an eye towards improved conventional and topological qubits. Chapters 1-3 focus on improved conventional (spin) qubits; Chapters 4-6 focus on the topological Majorana qubits. Chapter 1 presents the first investigation of Coulomb peak height distributions in a spin-orbit coupled quantum dot, realized in a Ge/Si nanowire. Strong spin-orbit coupling in this hole-gas system leads to antilocalization of Coulomb blockade peaks, consistent with theory. In particular, the peak height distribution has its maximum away from zero at zero magnetic field, with an average that decreases with increasing field. Magnetoconductance in the open-wire regime places a bound on the spin-orbit length (lso < 20 nm), consistent with values extracted in the Coulomb blockade regime (lso < 25 nm). Chapters 2 & 3 demonstrate operation of improved spin qubits. Chapter 2 continues the investigation of Ge/Si nanowires, demonstrating a qubit with tenfold-improved dephasing time compared to the standard GaAs case. e combination of long dephasing time and strong spin-orbit coupling suggests that Ge/Si nanowires are promising for a spin-orbit qubit. In Chap. 3, multi-electron spin qubits are operated in GaAs, and improved resilience to charge noise is found compared to the single-electron case. Chapters 4 & 5, present a series of studies on composite superconductor/semiconductor Al/InAs quantum dots. Detailed study of transport cycles and Coulomb blockade peak spacings in zero magnetic field are presented in Chap. 4, and the parity lifetime of a bound state in the nanowire is inferred to exceed 10 milliseconds. Next, in Chap. 5, finite magnetic field behavior is investigated while varying quantum dot length. Coulomb peak spacings are consistent with the emergence of Majorana modes in the quantum dot. The robustness of Majorana modes to magnetic-field perturbations is measured, and is found to be exponential with increasing nanowire length. Coulomb peak heights are also investigated, and show signatures of electron teleportation by Majorana fermions. Finally, Chap. 6 outlines some schemes to create topological Majorana qubits. Using experimental techniques similar to those in Chap.’s 2 & 3, it may be possible to demonstrate Majorana initialization, readout, and fusion rules.
Physics

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Allen, Monica Theresa. "Quantum Electronic Transport in Mesoscopic Graphene Devices". Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493258.

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Graphene provides a rich platform for the study of interaction-induced broken symmetry states due to the presence of spin and sublattice symmetries that can be controllably broken with external electric and magnetic fields. At high magnetic fields and low temperatures, where quantum effects dominate, we map out the phase diagram of broken symmetry quantum Hall states in suspended bilayer graphene. Application of a perpendicular electric field breaks the sublattice (or layer) symmetry, allowing identification of distinct layer-polarized and canted antiferromagnetic v=0 states. At low fields, a new spontaneous broken-symmetry state emerges, which we explore using transport measurements. The large energy gaps associated with the v=0 state and electric field induced insulating states in bilayer graphene offer an opportunity for tunable bandgap engineering. We use local electrostatic gating to create quantum confined devices in graphene, including quantum point contacts and gate-defined quantum dots. The final part of this thesis focuses on proximity induced superconductivity in graphene Josephson junctions. We directly visualize current flow in a graphene Josephson junction using superconducting interferometry. The key to our approach involves reconstruction of the real-space current density from magnetic interference using Fourier methods. We observe that current is confined to the crystal boundaries near the Dirac point and that edge and bulk currents coexist at higher Fermi energies. These results are consistent with the existence of "fiber-optic" edge modes at the Dirac point, which we model theoretically. Our techniques also open the door to fast spatial imaging of current distributions along more complicated networks of domains in larger crystals.
Physics

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Simmons, Stephanie. "Creation and control of entanglement in condensed matter spin systems". Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:b9c5ad90-30e2-4e44-8c51-37d46eabc92f.

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The highly parallel nature of the fundamental principles of quantum mechanics means that certain key resource-intensive tasks --- including searching, code decryption and medical, chemical and material simulations --- can be computed polynomially or even exponentially faster with a quantum computer. In spite of its remarkably fast development, the field of quantum computing is still young, and a large-scale prototype using any one of the candidate quantum bits (or 'qubits') under investigation has yet to be developed. Spin-based qubits in condensed matter systems are excellent candidates. Spins controlled using magnetic resonance have provided the first, most advanced, and highest fidelity experimental demonstrations of quantum algorithms to date. Despite having highly promising control characteristics, most physical ensembles investigated using magnetic resonance are unable to produce entanglement, a critical missing ingredient for a pure-state quantum computer. Quantum objects are said to be entangled if they cannot be described individually: they remain fundamentally linked regardless of their physical separation. Such highly non-classical states can be exploited for a host of quantum technologies including teleportation, metrology, and quantum computation. Here I describe how to experimentally create, control and characterise entangled quantum ensembles using magnetic resonance. I first explore the relationship between entanglement and quantum metrology and demonstrate a sensitivity enhancement over classical resources using molecular sensors controlled with liquid-state nuclear magnetic resonance. I then examine the computational potential of irreversible relaxation processes in combination with traditional reversible magnetic resonance control techniques. I show how irreversible processes can polarise both nuclear and electronic spins, which improves the quality of qubit initialisation. I discuss the process of quantum state tomography, where an arbitrary quantum state can be accurately measured and characterised, including components which go undetected using traditional magnetic resonance techniques. Lastly, I combine the above findings to initialise, create and characterise entanglement between an ensemble of electron and nuclear spin defects in silicon. I further this by generating pseudo-entanglement between an ensemble of nuclear spins mediated by a transient electron spin in a molecular system. These findings help pave the way towards a particular architecture for a scalable, spin-based quantum computer.

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19

Darmawan, Andrew. "Quantum computational phases of matter". Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/11640.

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Universal quantum computation can be realised by measuring individual particles in a specially entangled state of many particles, called a universal resource state. This model of quantum computation, called measurement-based quantum computation (MBQC), provides a framework for studying the intrinsic computational power of physical systems. In this thesis I will investigate how universal resource states may arise naturally as ground states of interacting spin systems. In particular, I will describe new 'phases' of quantum matter, which are characterised by having universal resource states as ground states. This direction of research allows us to draw on techniques from both many-body quantum physics and quantum information theory.

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20

Finnie, Paul D. "The fabrication and optical properties of quantum wires". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq26116.pdf.

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21

Sahnoune, Abdelhadi. "Quantum corrections to the conductivity in disordered conductors". Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39541.

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Quantum corrections to the conductivity have been studied at low temperatures down to 0.15K and fields up to 8.8T in two different disordered systems, namely amorphous Ca-Al alloys doped with Ag and Au and icosahedral Al-Cu-Fe alloys. In the former the influence of spin-orbit scattering on the enhanced electron-electron contribution to the resistivity has been, for the first time, clearly displayed. As the spin-orbit scattering rate increases, this contribution decreases rapidly to finally vanish at extremely high spin-orbit scattering rates. Furthermore the analysis shows that the current weak localization theory gives an accurate description of the experiments irrespective of the level of spin-orbit scattering.
In icosahedral Al-Cu-Fe alloys, detailed study of the low temperature resistivity shows that the magnetoresistance and the temperature dependence of the resistivity data are consistent with the predictions of quantum corrections to the conductivity theories. The success of these theories in this alloy system is attributed to intense electron scattering due to disorder. The spin-orbit scattering and the electron wave-function dephasing rates are extracted from fitting the magnetoresistance. The dephasing rate is found to vary as AT$ sp{p}$ with $p sim1.5$; a characteristic of electron-electron scattering in the strong disorder limit. An antilocalization effect has also been directly observed in the temperature dependence of the resistivity in one of the samples.

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22

Kou, Angela. "Microscopic Properties of the Fractional Quantum Hall Effect". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11161.

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The fractional quantum Hall effect occurs when an extremely clean 2-dimensional fermion gas is subject to a magnetic field. This simple set of circumstances creates phenomena, such as edge reconstruction and fractional statistics, that remain subjects of experimental study 30 years after the discovery of the fractional quantum Hall effect. This thesis investigates the properties of excitations of the fractional quantum
Physics

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23

Lee, Junhyun. "Novel Quantum Phase Transitions in Low-Dimensional Systems". Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493318.

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We study a number of quantum phase transitions, which are exotic in their nature and separates non-trivial phases of matter. Since quantum fluctuations, which drive these phase transitions, are stronger in low-dimensions, we concentrate on low-dimensional systems. We consider two different two-dimensional systems in this thesis and study their phase transition. First, we investigate a phase transition in graphene, one of the most famous two-dimensional systems in condensed matter. For a suspended bilayer graphene in ν = 0 quantum Hall regime, the conductivity data and mean-field analysis suggests a phase transition from an antiferromagnetic (AF) state to a valence bond solid (VBS) state, when perpendicular electric field is increased. This AF to VBS phase transition is reminiscent of deconfined criticality, which is a novel phase transition that cannot be explained by Landau’s theory of symmetry breaking. We show that in the strong coupling regime of bilayer graphene, the AF state is destabilized by the transverse electric field, likely resulting in a VBS state. We also consider monolayer and bilayer graphene in the large cyclotron gap limit and show that the effective action for the AF and VBS order parameters have a topological Wess-Zumino-Witten term, supporting that the phase transition observed in experiments is in the deconfined criticality class. Second, we study the model systems of cuprate superconductor, which is effectively a two-dimensionalal system in the CuO_2 plane. The proposal that the pseudogap metal is a fractionalized Fermi liquid described by a quantum dimer model is extended using the density matrix renormalization group. Measuring the Friedel oscillations in the open boundaries reveals that the fermionic dimers have dispersion minima near (π/2,π/2), which is compatible with the Fermi arcs in photoemission. Moreover, investigating the entanglement entropy suggests that the dimer model with low fermion density is similar to the free fermion system above the Lifshitz transition. We also study the phase transition from a metal with SU(2) spin symmetry to an AF metal. By applying the functional renormalization group to the two-band spin-fermion model, we establish the existence of a strongly coupled fixed point and calculate critical exponents of the fixed point.
Physics

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24

Lvov, Yuri Victorovich 1969. "Quantum weak turbulence with applications to semiconductor lasers". Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282713.

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Based on a model Hamiltonian appropriate for the description of fermionic systems such as semiconductor lasers, we describe a natural asymptotic closure of the BBGKY hierarchy in complete analogy with that derived for classical weak turbulence. The main features of the interaction Hamiltonian are the inclusion of full Fermi statistics containing Pauli blocking and a simple, phenomenological, uniformly weak two particle interaction potential equivalent to the static screening approximation. The resulting asymytotic closure and quantum kinetic Boltzmann equation are derived in a self consistent manner without resorting to a priori statistical hypotheses or cumulant discard assumptions. We find a new class of solutions to the quantum kinetic equation which are analogous to the Kolmogorov spectra of hydrodynamics and classical weak turbulence. They involve finite fluxes of particles and energy across momentum space and are particularly relevant for describing the behavior of systems containing sources and sinks. We explore these solutions by using differential approximation to collision integral. We make a prima facie case that these finite flux solutions can be important in the context of semiconductor lasers. We show that semiconductor laser output efficiency can be improved by exciting these finite flux solutions. Numerical simulations of the semiconductor Maxwell Bloch equations support the claim.

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25

Ramanathan, Swati. "Polarization Studies of Coupled Quantum Dots". Ohio University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1194984001.

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26

Riel, Bruno J. "Mechanisms governing the growth of self-assembled quantum dots". Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6448.

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We produced self-assembled quantum dot (QD) samples of InAs on GaAs by molecular beam epitaxy (MBE). With these, we explored growth effects as a function of InAs coverage for three arsenic pressures, and as a function of arsenic pressure at a specific InAs coverage. During growth, the samples were studied using reflection high energy electron diffraction (RHEED). These RHEED measurements were compared to low energy electron diffraction (LEED) measurements. To perform this ex-situ LEED characterisation, some samples were covered with an amorphous arsenic cap. This cap was thermally evaporated producing a clean, non-oxidised surface that was studied using LEED. We obtained non-ambiguous identification of the GaAs (001) surface reconstructions as well as timing information for the 2D to 3D transition during the growth of InAs on GaAs. Post growth characterisation of two sets of self-assembled QD samples, twelve samples in all, revealed the following: As a function of increasing the arsenic pressure used in QD growth, the photoluminescence (PL) of capped QDs is first redshifted at low arsenic pressures, and then blueshifted at high arsenic pressures. Scanning electron microscopy and atomic force microscopy of uncapped QDs show that as the arsenic pressure increases, the QD density increases while the average QD width and height decrease monotonically; these trends are consistent with the shift in PL for the high arsenic pressure samples, but are inconsistent with the shift in PL for the low pressure samples. This leads us to proposing a mechanism by which QDs may be modified as they are overgrown with capping material. We discuss the effects of adjusting the arsenic pressure on the formation of QDs and the mechanism by which QDs may be modified during capping.

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27

Yan, Zhi Da. "Energy level statistics for ballistic and mesoscopic quantum systems". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40022.

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Systems modelling nanoscale structures have been studied in the context of the theory of energy level statistics in the ballistic and mesoscopic as well as the insulating regimes. Statistics were obtained using a new unfolding scheme based on the existence of a local stationary property for fluctuations of the energy spectra. Two different models were used in the study with particular emphasis on the relevance to the physics of nanoscale devices. Thus, a quantum billiard model composed of a quasi-two-dimensional tight-binding atomic lattice was introduced. The results of the statistical analysis of the spectra of the models were compared throughout the thesis with Random Matrix Theory (RMT). The applicability of RMT and the universality predicted by RMT were verified.
The statistical behavior of energy levels for systems in the crossover region between regular and chaotic behavior was studied in all three regimes. Gradual transitions were observed for both ballistic and mesoscopic systems, and found to be similar in the cases. For systems in the insulating regime, the statistical behavior of levels was found to be of Poisson type. The transition from GOE to Poisson behavior when the system is changed from the mesoscopic to the insulating regime was also studied, a spectral dependence of the local fluctuations of energy levels was found, indicating the break-down of translation invariance of the local fluctuations.
The transition due to time reversal invariant symmetry breaking was studied by applying a uniform magnetic field to systems constructed by using a tight-binding model with non-zero off-diagonal interactions. By rescaling the transition control parameter, it was found that for both ballistic and mesoscopic systems the transition behavior can be well described by RMT. For closed systems the transition is complete when the effective area of the system encloses a flux greater than one flux quantum.

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28

Steele, Andrew J. "Quantum magnetism probed with muon-spin relaxation". Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:030d7e91-f38e-433f-9539-652b0f4996cc.

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This thesis presents the results of muon-spin relaxation (µ⁺SR) studies into magnetic materials, and demonstrates how these results can be exploited to quantify the materials’ low moments and reduced dimensionality. Dipole-field simulations, traditionally used to estimate likely muon sites within a crystal structure, are described. A novel Bayesian approach is introduced which allows bounds to be extracted on magnetic moment sizes and magnetic structures—previously very difficult using µ⁺SR—based on reasonable assumptions about positions in which muons are likely to stop. The simulations are introduced along with relevant theory, and MµCalc, a platform-independent program which I have developed for performing the calculations is described. The magnetic ground states of the isostructural double perovskites Ba₂NaOsO₆ and Ba₂LiOsO₆ are investigated with µ⁺SR. In Ba₂NaOsO₆ long-range magnetic order is detected via the onset of a spontaneous muon-spin precession signal below T_c = 7.2(2) K, while in Ba₂LiOsO₆ a static but spatially-disordered internal field is found below 8 K. Bayesian analysis is used to show that the magnetic ground state in Ba₂NaOsO₆ is most likely to be low-moment (˜ 0.2µ_B) ferromagnetism and not canted antiferromagnetism. Ba₂LiOsO₆ is antiferromagnetic and a spin-flop transition is found at 5.5 T. A reduced osmium moment is common to both compounds, probably arising from a combination of spin–orbit coupling and frustration. Results are also presented from µ⁺SR investigations concerning magnetic ordering in several families of layered, quasi–two-dimensional molecular antiferromagnets based on transition metal ions such as S = ½ Cu²⁺ bridged with organic ligands such as pyrazine. µ⁺SR allows us to identify ordering temperatures and study the critical behaviour close to T_N , which is difficult using conventional probes. Combining this with measurements of in-plane magnetic exchange J and predictions from quantum Monte Carlo simulations allows assessment of the degree of isolation of the 2D layers through estimates of the effective inter-layer exchange coupling and in-layer correlation lengths at T_N. Likely metal-ion moment sizes and muon stopping sites in these materials are identified, based on probabilistic analysis of dipole-fields and of muon–fluorine dipole–dipole coupling in fluorinated materials.

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29

Jha, Shantenu Middleton A. Alan. "Numerical studies of electron transport in disordered quantum dot arrays". Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2004. http://wwwlib.umi.com/cr/syr/main.

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30

Vachon, Martin. "Optical properties of single quantum dots in high magnetic field". Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/28029.

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The photoluminescence of quantum dots is studied in a high magnetic field regime where the cyclotron frequency is comparable to the confinement energy. Applying a magnetic field perpendicular to the lateral potential plane lifts the shell degeneracy and magneto-photoluminescence spectroscopy therefore provides a probe to investigate the energy shell structure of quantum dots. By isolating a single quantum dot, the inhomogeneous broadening from a distribution of dot sizes and compositions is eliminated and the fine structure of the spectrum is revealed. The orbital splitting of angular momentum states is shown to follow the Fock-Darwin scheme. However, it is also apparent that each angular momentum branch consists of two distinct lines whose magnetic field evolution cannot be explained by a simple Zeeman spin splitting. The dependence of line splitting on orbital state can be described by the addition of spin-orbit coupling to the Fock-Darwin model. Accordingly, a quantitative measurement of the spin-orbit coupling strength in self-assembled quantum dots is obtained for the first time.

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31

Ji, Tao 1981. "Kondo resonance in double quantum dots : a Green's function analysis". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84042.

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In this thesis, an overview of non-equilibrium Green's function (NEGF) technique is presented. The entire formulism is derived from the starting point of the definitions of Green's functions. The special application of NEGF to transport problems is discussed in details. A brief introduction of Kondo phenomenon and several theoretical approaches are presented. Using the knowledge of NEGF and Kondo problem in general, we investigated the Kondo phenomenon in double quantum dots (DQD) in great detail. In this application, the physical quantities are derived in terms of Green's functions and self-consistent equations determining the state of the system are solved numerically. A phase diagram is presented as the result of competition between Kondo effect and magnetic exchange interaction, and spin flipping scattering center in the DQD system is shown to have great effect as it breaks the coherence between the two QDs under certain circumstances.

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32

Lei, Ming. "Quantum hall effect in the presence of an antidot potential". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23910.

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The crossover transport regime between the quantum Hall effect and the Aharonov-Bohm effect is studied in terms of Buttiker's approach of electrical conduction. Quantum Hall effect and Aharonov-Bohm effect are very important effects in mesoscopic physics and both demonstrate unambiguously that quantum mechanics is the dominant factor in nanoscale electrical transport problems. However, they belong to situations of different dimensionality and different strength of magnetic fields. Our goal is to reveal the physics at the crossover regime between the two and find the transport properties of this transition regime.
We have computed Hall resistance of a four-probe box-shaped quantum dot with an artificial impurity confined inside. As the size of the impurity is increased, transport behavior changes from the usual quantum Hall regime to a regime dominated by strong Aharonov-Bohm (AB) oscillations. We observe directly the formation and coupling of the edge states and their effects on the Hall resistance, by varying a magnetic field. For a range of the impurity size, transport enters the crossover regime where quantum Hall and AB effects compete, and a peculiar approximate symmetry between various transmission coefficients lead to a Hall plateau before the quantum Hall regime is reached. This symmetry can be explained based on scattering matrix theory and a topological equivalence of the dominating transmission patterns where well defined edge states are formed. Finally we investigate the universality of the observed symmetry property in several other structures and find that within the scope of our calculation the symmetry is universal.

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33

Li, Cheng. "Engineering High Dimensional Topological Matters in Quantum Gases". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1585827770946136.

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34

Zhang, Bo. "Quantum turbulence in two dimensional Bose-Einstein condensates". W&M ScholarWorks, 2011. https://scholarworks.wm.edu/etd/1539623584.

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We examine the energy cascades and quantum vortex structures in two-dimensional quantum turbulence through a special unitary time evolution algorithm. An early attempt at using the Lattice Boltzmann Method proved successful in correctly representing some features of the Nonlinear Schrodinger System (NLS), such as the phase shift following the one-dimensional soliton-soliton collision, as well as the two-dimentional modulation instability. However, to accurately evaluate NLS, the implicit Euler method is required to resolve the time evolution, which is computationally expensive. A more accurate and efficient method, the Quantum Lattice Gas model is employed to simulate the quantum turbulence governed by the Gross-Pitaevskii equation, an equaiton that describes the evolution of the ground state wave function for a Bose-Einstein condensate (BEC). It is discovered that when the ratio of the internal energy to the kinetic energy is below 0.05, an unexpected short Poincare recurrence occurs independent of the initial profile of the wave function. It is demonstrated that this short recurrence is destroyed as the internal energy is strengthened. to compare the two-dimensional quantum turbulence with its classical counterpart, the incompressible energy spectra of quantum turbulence is analyzed. However, the result reveals no sign of dual cascades which is a hallmark of the classical incompressible two-dimensional fluid (inverse energy cascade to large scales with a direct cascade of enstrophy to small scales). It is the spectra of the compressible energy that can exhibits multiple cascades, but this is strongly dependent on the initial condition.

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35

Guiang, Chona Siota. "Quantum control of I₂ photodissociation in gas phase and condensed phase environments /". Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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36

Wang, Ye. "Photoelectronic study of GaAs epilayers and InxGa1-xAs/GaAs quantum wells". Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7883.

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The photoelectromagnetic (PEM) effect was used to perform experiments on photocarriers' transport properties in GaAs substrates and epitaxial layers. For the undoped semi-insulating substrate, the carriers' mobility $\mu$ at T = 77K was measured by PEM effect method, giving a value of $\mu$ = 40,000 cm$\sp2$ V$\sp{-1}$s$\sp{-1}$. It was found that the carriers' diffusion length is L$\sb{\rm D}$ = 0.27 $\mu$m at T = 300K and L$\sb{\rm D}$ = 0.44 $\mu$m at T = 77K. For the 3.4$\mu$m thick epitaxial layer grown by metal-organic chemical vapour deposition (MOCVD), the carriers' diffusion length was measured to be L$\sb{\rm D}$ = 2.6 $\mu$m at T = 300K, L$\sb{\rm D}$ = 3.1 $\mu$m at T = 77K and L$\sb D \approx$ 3.5 $\mu$m at T = 5K. A photocurrent (PC) spectroscopy study of In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As/GaAs quantum wells on Cr-doped and undoped substrates has been performed. Several well-resolved structures related to inter-subband transitions are observed in the photoconductivity spectra for both T = 300K and T = 77K, and they are in good agreement with calculation taking into account the strain-induced splitting of the bands. Both Cr-doped and undoped substrates have been found to influence the results, as shown by optical quenching techniques.

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37

Haysom, Joan E. "Quantum well intermixing of indium gallium arsenide(phosphorus)/indium phosphorus heterostructures". Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9400.

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This thesis studies several aspects of the interdiffusion of InGaAs(P)/InP quantum well (QW) heterostructures, from the fundamental defect mechanisms, through optimization of processing parameters, to novel device applications. Conclusions from each of these areas have been drawn which further the scientific understanding and the manufacturability of the technique. The thermal stability of a series of different wafers is studied to highlight how poor quality of growth can cause increased interdiffusion, and to review the requirements for achieving repeatable annealing. Purposeful and controlled interdiffusion is accomplished through the introduction of excess defects into layers above the QWs, which during a subsequent anneal, diffuse through the QWs and enhance interdiffusion of atoms of the QWs with atoms of the barriers. These excess defects are introduced using two different techniques, via growth at low temperatures (LT) using chemical beam epitaxy (CBE), and via implantation of phosphorus ions. The CBE LT growth technique is new, and reported for the first time in this thesis. Characterization of the as-grown layers leads us to believe that they have an excess of phosphorus. The diffusion rate of the mobile defects which cause the intermixing is also measured, and the interdiffusion is shown to occur predominantly on the group-V sublattice. Due to many similarities between this and the results of the implantation technique, it is proposed that these mobile defects are the same for both intermixing approaches, and that the behaviour can be explained by a phosphorus interstitial mechanism. Annealing recipes for the implantation-induced technique are optimized, and the sample-to-sample reproducibility of the blueshift for this method was found to be quite good (standard deviations of ∼6 meV on blueshifts of ∼70 meV). The lateral selectivity and refractive index changes are characterized, and used in combination to create novel buried waveguide devices.

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38

Piva, Paul Garrett. "A photoluminescence study of intermixed III/V semiconductor quantum well structures". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq26357.pdf.

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39

Chowdhury, Debanjan. "Interplay of Broken Symmetries and Quantum Criticality in Correlated Electronic Systems". Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493455.

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This thesis delves into a study of phases of strongly correlated quantum matter confined to two spatial dimensions. The thesis can broadly be divided into three parts. In the first part, comprising of chapters 2 and 3, we investigate some interesting aspects of symmetry breaking and quantum criticality in the superconducting phase of the iron-based superconductors. In particular, motivated by tunneling microscopy measurements on FeSe, in chapter 2 we study the effect of spontaneously broken rotational symmetry on the structure of the superconducting vortex. In chapter 3, we study the critical singularities associated with the superfluid-density at a wide class of symmetry-breaking and topological phase transitions in a clean superconductor. Inspired by experiments on BaFe$_2$(As$_{1-x}$P$_x$)$_2$, we also analyze the effect of quenched disorder on the superfluid-density in the vicinity of magnetic quantum critical points. The second part of this thesis, consisting of chapters 4 and 5, is devoted to a study of the pseudogap phase in the underdoped cuprates. In chapter 4 we study the effect of thermal fluctuations of various competing order parameters, including preformed superconductivity and short-ranged charge-density wave, on the electronic excitations. In chapter 5 we analyze the feedback of pairing fluctuations on the landscape of various competing charge-density wave order parameters within the framework of fermi-liquid theory. In the final part of the thesis, consisting of chapters 6 and 7, we propose an alternative picture for describing the pseudogap metal. In chapter 6, we study a quantum-disordered phase of matter---the fractionalized fermi-liquid (FL*)---where the electrons are coupled to the fractionalized excitations of a strongly fluctuating antiferromagnet and propose it to be a candidate state for the pseudogap. We investigate instabilities of the FL* to density-wave order and compare with experiments. In chapter 7, we describe a framework for describing a novel quantum phase transition without any broken-symmetries---a Higgs transition---that describes a transition from a conventional fermi-liquid to a parent phase of the FL* state via an intermediate non-fermi liquid. We discuss its possible connection to the optimal doping critical point in the cuprates.
Physics

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40

Collins, Alexander Rory Physics Faculty of Science UNSW. "Quantum lattice models". Publisher:University of New South Wales. Physics, 2008. http://handle.unsw.edu.au/1959.4/43408.

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This thesis presents studies of the low energy properties of nseveral frustrated spin-1/2 Heisenberg antiferromagnets using various analytic and computational methods. The models studied include the union jack model, the alternating Heisenberg chain, the Heisenberg bilayer model, and the spin-Peierls model. The union jack model is a Heisenberg antiferromagnetic spin model with frustration, and is analyzed using spin-wave theory. For small values of the frustrating coupling $\alpha$, the system is N{\' e}el ordered, while for large $\alpha$ the frustration is found to induce a canted phase. Spin wave theory with second order corrections finds the critical coupling at $\alpha \simeq 0.645$,which agrees quantitatively with series expansion results. No intermediate spin-liquid phase is found to exist between the two phases. The alternating Heisenberg chain is studied using an alternative triplet-wave expansion formalism for dimerized spin systems, modification of the ??bond operator?? formalism of Sachdev and Bhatt. Projection operators are used to confine the system to the physical subspace, rather than constraint equations. Comparisons are made with the results of dimer series expansions and exact diagonalization. The S=1/2 Heisenberg bilayer spin model at zero temperature is studied in the dimerized phase using analytic triplet-wave expansions and dimer series expansions. The occurrence of two-triplon bound states in the S=0 and S=1 channels, and antibound states in the S=2 channel, is predicted with triplet-wave theory and confirmed by series expansions. All bound states are found to vanish at or before the critical coupling separating the dimerized phase from the N{\' e}el phase. The critical behavior of the total and single-particle static transverse structure factors is also studied by series expansion methods and found to conform with theoretical expectations. The Heisenberg spin-Peierls model with dispersive, gapless phonons is studied with Density Matrix Renormalization Group methods. We investigate the zero temperature properties of the model using the crossover method. The calculations were found to converge poorly and no conclusive results could be found using this method. An analysis of the convergence problems and the discovery of an anomalous triplet ground state is presented in this chapter.

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41

Matis, Bernard Richard. "Electron Transport in GaAs Quantum Dots under High Frequencies". Diss., Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/107155.

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Physics
Ph.D.
This thesis explores transport properties of lateral, gate defined quantum dots in GaAs/AlGaAs heterostructures. The term "quantum dot" as defined in this thesis refers to small regions of charge carriers within a 2-dimensional electron gas (2DEG), established via electrically biased surface gates used to isolate the charge carriers from the rest of the 2DEG, which are confined to lengths scales on the order of nanometers. Several other forms of quantum dots exist in the research community, including colloidal and self-assembled dots. In this thesis, however, we consider only gate defined quantum dots and nanostructures. Recent advancements in the research areas of quantum dot (QD) and single electron transistors (SET) have opened up an exciting opportunity for the development of nanostructure devices. Of the various devices, our attention is drawn in particular to detectors, which can respond to a single photon over a broad frequency spectrum, namely, microwave to infrared (IR) frequencies. Here, we report in chapter 5 transport measurements of parallel quantum dots, fabricated on a GaAs/AlGaAs 2-dimensional electron gas material, under the influence of external fields associated with 110GHz signals. In this experiment, transport measurements are presented for coupled quantum dots in parallel in the strong-tunneling Coulomb blockade (CB) regime. From this experiment we present experimental results and discuss the dependence on quantum dot size, fabrication techniques, as well as the limitations in developing a QD photon detector for microwave and IR frequencies, whose noise equivalent power (NEP) can be as sensitive as 10-22 W/Hz1/2. The charging energy EC of a quantum dot is the dominant term in the Hamiltonian and is inversely related to the self capacitance of the dot Cdot according to EC = e2/Cdot. The temperature of the charge carriers within the 2DEG must be kept below a certain value, namely KBT, so that the thermal energy of the electrons does not exceed the charging energy EC of the dot. Keeping the temperature below the KBT limit prevents electrons from entering or leaving the dot at random, thereby allowing one to precisely control the number of electrons in the dot. In order to raise the operating temperature T of the single photon detector we must also raise the charging energy EC, which is accomplished by decreasing Cdot. Since Cdot is directly related to the dimensions of the quantum dot our focus was directed at decreasing the overall size of the quantum dots. For smaller gate defined quantum dots the inclusion of shallower 2DEG's is necessary. However, the experiments that we carried out to determine the effect of 2DEG depth on lateral gate geometries, described in Chapter 6, indicate that leakage currents within a GaAs/AlGaAs heterostructure increased dramatically as the 2DEG depth became shallower. At this moment the leakage current in shallower 2DEG materials is one of the most significant technical challenges in achieving higher operating temperatures of the single photon detector.
Temple University--Theses

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42

Lam, Jennifer Eleanor. "The nature of the metal-insulator transition in silicon germanide quantum wells". Thesis, University of Ottawa (Canada), 1997. http://hdl.handle.net/10393/4399.

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A study of the temperature dependence of the resistivity of gated SiGe quantum well structures has revealed a metal-insulator transition as a function of carrier density at zero magnetic field. Although early scaling theories (Abrahams et al., 1979) have argued against the existence of a metal-insulator transition at zero temperature in infinite 2D and 1D systems, more recent theoretical results using a random set of two-dimensional point potentials have shown that such a transition is allowed in two dimensions (Az'bel, 1992). Mounting experimental evidence for such a transition in 2D systems with short range scattering has accumulated in both semiconducting and superconducting structures (Kravchenko et al., 1995, and others). Pseudomorphic, CVD-grown p-type Si/Si$\sb{0.87}$Ge$\sb{0.13}$/Si quantum wells of various widths (65-200 A) have been studied. The samples were gated using a Ti-Au Schottky gate to allow for carrier density variation. Measurement of the transport to quantum lifetime ratio indicates that the transport is dominated by short range scattering. In the temperature range from 400 mK - 4.2 K, the temperature dependence shows a transition from a metallic phase in the high density regime to an insulating phase in the low density regime with a transition boundary close to 2.2 $\times$ 10$\sp $ cm$\sp{-2}$. The scaling properties of the observed metal-insulator transition will be discussed, and compared to previous scaling results from silicon MOSFETs. Below 400 mK, the onset of another transition is accompanied by a sharp drop in resistivity with temperature followed by a monotonic decrease in resistivity below 115 mK. The phase diagram was explored using temperature and density dependences of the current-voltage characteristics.

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43

Agarwal, Kartiek. "Slow Dynamics in Quantum Matter: The Role of Dimensionality, Disorder and Dissipation". Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493505.

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A central goal in the study of modern condensed matter physics is the characterization of the dynamical properties of quantum systems. Many decades of effort towards this goal, studying a diverse range of (near-equilibrium) quantum matter, from Fermi liquids, to quantum two-level systems, to interacting spin models, and more, has revealed a remarkable pervasiveness of the simple dynamical description of these complex systems in terms of quasi-particles that carry spin, charge, and heat, and that are generally able to equilibrate systems. This thesis is an examination of some exceptions to this rule. Specifically, we study a number of instances of quantum matter where equilibration phenomena happens at rather long time scales, or does not occur at all. Particular emphasis is laid on the role of dimensionality, disorder, and dissipation in engendering such novel dynamical behavior. First, we consider non-equilibrium dynamics in one-dimensional quasi-condensates. Low dimensionality inhibits scattering in these systems, and low-energy excitations are long-lived phase fluctuations that exhibit an enriched conformal symmetry. Utilizing this symmetry, we generalize sudden quenches typically used to study non-equilibrium dynamics to quenches along general relativistic and conformal trajectories. Gases never truly equilibrate after such a quench; instead, they evolve into a `prethermal' state with thermal-looking correlations and a chiral asymmetry. We then study the problem of the dynamical transition driven by disorder, from an ergodic to a non-ergodic phase, in one-dimensional quantum spin chains. In particular, in XXZ chains with on-site disorder, we find a unique intermediate phase straddling the boundary of the dynamical phase transition, wherein rare-region effects lead to long-time tails in equilibration and vanishing DC conduction before the onset of non-ergodicity. We propose generalizations of such `Griffiths' behavior to arbitrary dimensions. We also study the dynamics of random-bond Heisenberg chains by developing a strong-disorder renormalization group protocol for these systems. We discuss how magnetic noise from such disordered systems contains signatures of their anomalous dynamical properties. Next, we re-examine the phenomenological theory of two-level systems in amorphous materials in the light of new experimental evidence that these states have large electric/magnetic dipole moments. We propose and justify an interpretation of the model as one of tunneling electrons slowed down by a large phonon drag and discuss the dynamical consequences of such polaronic effects. Finally, we discuss how magnetic noise measurements can be used to non-invasively access the anomalous properties of systems such as those discussed above. In particular, we examine how scattering properties of isolated magnetic impurities and non-local transport in a variety of two-dimensional materials can be probed experimentally using NV centers as noise magnetometers.
Physics

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44

Bernstein, Lisa Joan. "Quantum theories of self-localization". Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/298722.

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In the classical dynamics of coupled oscillator systems, nonlinearity leads to the existence of stable solutions in which energy remains localized for all time. Here the quantum-mechanical counterpart of classical self-localization is investigated in the context of two model systems. For these quantum models, the terms corresponding to classical nonlinearities modify a subset of the stationary quantum states to be particularly suited to the creation of nonstationary wavepackets that localize energy for long times. The first model considered here is the Quantized Discrete Self-Trapping model (QDST), a system of anharmonic oscillators with linear dispersive coupling used to model local modes of vibration in polyatomic molecules. A simple formula is derived for a particular symmetry class of QDST systems which gives an analytic connection between quantum self-localization and classical local modes. This formula is also shown to be useful in the interpretation of the vibrational spectra of some molecules. The second model studied is the Frohlich/Einstein Dimer (FED), a two-site system of anharmonically coupled oscillators based on the Frohlich Hamiltonian and motivated by the theory of Davydov solitons in biological protein. The Born-Oppenheimer perturbation method is used to obtain approximate stationary state wavefunctions with error estimates for the FED at the first excited level. A second approach is used to reduce the first excited level FED eigenvalue problem to a system of ordinary differential equations. A simple theory of low-energy self-localization in the FED is discussed. The quantum theories of self-localization in the intrinsic QDST model and the extrinsic FED model are compared.

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45

Valente, Diego. "DECOHERENCE IN SEMICONDUCTOR SOLID-STATE QUANTUM COMPUTERS". Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2797.

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In this dissertation we discuss decoherence in charge qubits formed by multiple lateral quantum dots in the framework of the spin-boson model and the Born-Markov approximation. We consider the intrinsic decoherence caused by the coupling to bulk phonon modes and electromagnetic environmental fluctuations. In the case of decoherence caused by phonon coupling, two distinct quantum dot configurations are studied and proposed as setups that mitigate its nocive effects : (i) Three quantum dots in a ring geometry with one excess electron in total and (ii) arrays of quantum dots where the computational basis states form multipole charge configurations. For the three-dot qubit, we demonstrate the possibility of performing one- and two-qubit operations by solely tuning gate voltages. Compared to a previous proposal involving a linear three-dot spin qubit, the three-dot charge qubit allows for less overhead on two-qubit operations. For small interdot tunnel amplitudes, the three-dot qubits have Q factors much higher than those obtained for double-dot systems. The high-multipole dot configurations also show a substantial decrease in decoherence at low operation frequencies when compared to the double-dot qubit. We also discuss decoherence due to electromagnetic fluctuations in charge qubits formed by two lateral quantum dots. We use effective circuit models to evaluate correlations of voltage fluctuations in the qubit setup. These correlations allows us to estimate energy (T1) and phase (T2) relaxation times of the the qubit system. We also discuss the dependence the quality factor Q shows with respect to parameters of the setup, such as temperature and capacitive coupling between the electrodes.
Ph.D.
Department of Physics
Sciences
Physics PhD

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46

Worsley, Richard Edward. "Time-resolved relaxation processes in quantum wells". Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295867.

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47

Shojaei, Borzoyeh. "Antimonide-Based Compound Semiconductors for Quantum Computing". Thesis, University of California, Santa Barbara, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10195560.

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Quantum information science has made significant progress over the last several decades, but the eventual form a quantum computer will take has yet to be determined. Several physical systems have been shown to operate as quantum bits, or qubits, but each faces a central challenge: the qubit must be sufficiently isolated from its environment to maintain quantum coherence while simultaneously having sufficient coupling to the environment to allow quantum mechanical interactions for manipulation and measurement. An approach to achieve these conflicting requirements is to create qubits that are insensitive to small perturbing interactions within their environment by using topological properties of the physical system in which the qubits are formed. This dissertation presents studies on low-dimensional semiconductor heterostructures of InAs, GaSb and AlSb fabricated by molecular beam epitaxy with focus on relevant properties for their utilization in forming a topologically protected (TP) qubit.

The theoretical basis regarding the semiconductor characteristics suitable for realizing TP qubits stipulates the need for strong spin-orbit coupled semiconductors with high carrier mobility. A comparative study of InAs/AlSb heterostructures wherein structure parameters were systematically varied led to a greater understanding of the limits to mobility in InAs quantum wells. Magnetotransport measurements using a dual-gated device geometry and a comparison of experiment to models of carrier mobility as a function of carrier density were used to identify dominant scattering mechanisms in these heterostructures.

The development of dual-gated devices and high quality InAs channels with AlSb barriers led to a demonstration of the gate control of spin-orbit coupling in a high mobility InAs/AlSb quantum well in which the gate-tuned electron mobility exceeded 700,000 cm²/V·s. Analysis of low temperature magnetoresistance oscillations indicated the zero field spin-splitting could be tuned via the Rashba effect while keeping the two-dimensional electron gas charge density constant.

Findings from the work on InAs quantum wells were applied to investigations on InAs/GaSb bilayers, a system predicted to be a two-dimensional topological insulator (TI). The temperature and magnetic field dependence of the resistance in dual-gated InAs/GaSb heterostructures gate-tuned to the predicted TI regime were found consistent with conduction through a disordered two-fluid system. The impact of disorder on the formation of topologically protected edge states and an insulating bulk was considered. Potential fluctuations in the band structure for realistic levels of disorder in state-of-the-art heterostructures were calculated using a gated heterostructure model. Potential fluctuations were estimated to be sufficiently large such that conduction in the predicted TI regime was likely dominated by tunneling between localized electron and hole charge fluctuations, corresponding to a symplectic metallic phase rather than a topological insulator. The implications are that future efforts must address defects and disorder in this system if the TI regime is to be achieved.

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Schönherr, Piet. "Growth and characterisation of quantum materials nanostructures". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:7dca792e-4236-4d19-aa59-7c9c3cb5d0e4.

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The three key areas of this thesis are crystal synthesis strategies, growth mechanisms, and new types of quantum materials nanowires. The highlights are introduction of a new catalyst (TiO2) for nanowire growth and application to Bi2Se3, Bi2Te3, SnO2, and Ge nanowires; demonstration of step-flow growth, a new growth mechanism, for Bi2Te3 sub-micron belts; and the characterisation of the first quasi-one dimensional topological insulator (orthorhombic Sb-doped Bi2Se3) and topological Dirac semimetal nanowires (Cd3As2). Research into new materials has been one of the driving forces that have contributed to the progress of civilisation from the Bronze Age four thousand years ago to the age of the semiconductor in the 20^th century. At the turn to the 21^st century novel materials, so-called quantum materials, started to emerge. The fundamental theories for the description of their properties were established at the beginning of the 20^th century but expanded significantly during the last three decades based, for example, on a new interpretation of electronic states by topological invariants. Hence, topological insulator (TI) materials such as mercury-telluride are one manifestation of a quantum material. In theory, TIs are characterised by an insulating interior and a surface with spin-momentum locked conduction. In real crystals, however, the bulk can be conducting due to crystal imperfections. Nanowires suppress this bulk contribution inherently by their high surface-to-volume ratio. Additionally, trace impurity elements can be inserted into the crystal to decrease the conductance further. These optimised TI nanowires could provide building blocks for future electronic nanodevices such as transistors and sensors. Initial synthesis efforts using vapour transport techniques and electronic transport studies showed that TI nanowires hold the promise of reduced bulk contribution. This thesis expands the current knowledge on synthesis strategies, crystal growth mechanisms, and new types of quantum materials nanowires. Traditionally, gold catalyst nanoparticles were used to grow TI nanowires. We demonstrate that they are suitable to produce large amounts of nanowires but have undesired side-effects. If a metaloxide catalyst nanoparticle is used instead, quality and even quantity are significantly improved. This synthesis strategy was used to produce a new TI which is built from chains of atoms and not from atomic layers as in case of previously known TIs. The growth of large nanowires with a layered crystal structure leads to step-flowgrowth, an intriguing phenomenon in the growth mechanism: New layers grow on top of previous layers with a single growth frontmoving fromthe root to the tip. These wires are ideal for further electronic characterisation that requires large samples. The nanowire growth of tin-oxide will also be discussed, a side project that arose from my growth studies, which is useful for sensor applications. Under certain conditions it forms tree-like structures in a single synthesis step. All of the aforementioned growth studies are carried out at atmospheric pressure. A separate growth study is carried out in ultra-high vacuum to assess the transferability of the growth process towards the cleanliness requirements of the semiconductor industry. If two quantum materials are joined together, exotic physics may emerge at the interface. One of the goals of TI research is the experimental observation of Majorana fermions, exotic particles which are their ownantiparticles with potential applications in quantum computing that may appear in superconductor/TI hybrid structures. We have synthesised such structures and initial characterisation suggests that the resistivity increases when they are cooled below the critical temperature of the superconductor. Beyond TIs, a new type of quantum material, called a topological Dirac semimetal, opens new realms of exotic physics to be discovered. Nanowires are grownfroma material which has recently been discovered to be a topological Dirac semimetal. Their growth mechanism is characterised and an extremely high electron mobility at room temperature is measured. The contribution of this thesis to the field is summarised in Fig. 1. Its core is the study of the growth mechanism of quantum materials which will be vital for future development of applications and fundamental research.

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Chatterjee, Sangam. "Exciton formation dynamics in semiconductor quantum wells". Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280403.

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Photoluminescence from direct-bandgap semiconductor quantum wells after non-resonant excitation is predominantly observed at energetic position of the 1s exciton resonance. The time evolution of the photoluminescence is generally interpreted as direct monitor of an excitonic population; a rise of the signal is interpreted as a buildup and the decrease as decay of the excitonic population. Recent microscopic calculations, however, have shown that even without an incoherent excitonic population, pure plasma decay yields photoluminescence peaked at the is exciton resonance. Experimental time-resolved photoluminescence spectra are taken across a large region of the parameter space of carrier density and lattice temperature. They are compared to the expected thermal equilibrium spectra, calculated from nonlinear absorption measurements taken under identical conditions. Under none of the experimentally explored parameters is the is emission as bright as expected for thermal equilibrium. To distinguish excitonic and plasma contributions, the deviations from thermal equilibrium at the is exciton resonance are then analyzed using a microscopic calculation. The dipole moment is adjusted to reproduce the excitonic binding energy and oscillator strength of the samples under investigation. The carrier densities and carrier temperatures are determined experimentally; no free fit parameters are necessary. The differences between experimental values and pure plasma calculation are explained with the presence of an incoherent excitonic population. Although at first the emission spectra under all conditions do not vary significantly, a more detailed analysis reveals that the sources of the photoluminescence can be either predominantly excitonic or plasma. For low temperatures and low densities the excitonic emission is extremely sensitive to even minute exciton populations making it possible to extract a phase diagram for incoherent excitonic populations. The maximum contribution of bright excitons is found at intermediate densities and low lattice temperatures; the absolute number of bright excitons is tiny, less than 0.04% of the total carrier density. However, it is not possible to determine the total number of bright and dark exciton by using photoluminescence.

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Park, YeJe. "Guiding-center hall viscosity and intrinsic dipole moment of fractional quantum Hall states". Thesis, Princeton University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3665335.

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The fractional quantum Hall effect (FQHE) is the archetype of the strongly correlated systems and the topologically ordered phases. Unlike the integer quantum Hall effect (IQHE) which can be explained by single-particle physics, FQHE exhibits many emergent properties that are due to the strong correlation among many electrons. In this Thesis, among those emergent properties of FQHE, we focus on the guiding-center metric, the guiding-center Hall viscosity, the guiding-center spin, the intrinsic electric dipole moment and the orbital entanglement spectrum.

Specifically, we show that the discontinuity of guiding-center Hall viscosity (a bulk property) at edges of incompressible quantum Hall fluids is associated with the presence of an intrinsic electric dipole moment on the edge. If there is a gradient of drift velocity due to a non-uniform electric field, the discontinuity in the induced stress is exactly balanced by the electric force on the dipole.

We show that the total Hall viscosity has two distinct contributions: a "trivial'' contribution associated with the geometry of the Landau orbits, and a non-trivial contribution associated with guiding-center correlations.

We describe a relation between the intrinsic dipole moment and "momentum polarization'', which relates the guiding-center Hall viscosity to the "orbital entanglement spectrum(OES)''.

We observe that using the computationally-more-onerous "real-space entanglement spectrum (RES)'' in the momentum polarization calculation just adds the trivial Landau-orbit contribution to the guiding-center part. This shows that all the non-trivial information is completely contained in the OES, which also exposes a fundamental topological quantity γ = c˜ − ν, the difference between the "chiral stress-energy anomaly'' (or signed conformal anomaly) and the chiral charge anomaly. This quantity characterizes correlated fractional quantum Hall fluids, and vanishes in integer quantum Hall fluids which are uncorrelated.

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