Journal articles: 'Out-of-equilibrium quantum systems'

1

Eisert, J., M. Friesdorf, and C. Gogolin. "Quantum many-body systems out of equilibrium." Nature Physics 11, no. 2 (February 2015): 124–30. http://dx.doi.org/10.1038/nphys3215.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Garrido, Pedro L., Pablo Hurtado, Daniel Manzano, and Francisco de los Santos. "Quantum systems in and out of equilibrium." European Physical Journal Special Topics 227, no. 3-4 (September 2018): 201–2. http://dx.doi.org/10.1140/epjst/e2018-800100-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Brunelli, M., A. Xuereb, A. Ferraro, G. De Chiara, N. Kiesel, and M. Paternostro. "Out-of-equilibrium thermodynamics of quantum optomechanical systems." New Journal of Physics 17, no. 3 (March 31, 2015): 035016. http://dx.doi.org/10.1088/1367-2630/17/3/035016.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Maisel, Lucas, and Rosa López. "Effective Equilibrium in Out-of-Equilibrium Interacting Coupled Nanoconductors." Entropy 22, no. 1 (December 19, 2019): 8. http://dx.doi.org/10.3390/e22010008.

Full text

Abstract:

In the present work, we study a mesoscopic system consisting of a double quantum dot in which both quantum dots or artificial atoms are electrostatically coupled. Each dot is additionally tunnel coupled to two electronic reservoirs and driven far from equilibrium by external voltage differences. Our objective is to find configurations of these biases such that the current through one of the dots vanishes. In this situation, the validity of the fluctuation–dissipation theorem and Onsager’s reciprocity relations has been established. In our analysis, we employ a master equation formalism for a minimum model of four charge states, and limit ourselves to the sequential tunneling regime. We numerically study those configurations far from equilibrium for which we obtain a stalling current. In this scenario, we explicitly verify the fluctuation–dissipation theorem, as well as Onsager’s reciprocity relations, which are originally formulated for systems in which quantum transport takes place in the linear regime.

APA, Harvard, Vancouver, ISO, and other styles

5

Calabrese, Pasquale, Fabian H. L. Essler, and Giuseppe Mussardo. "Introduction to ‘Quantum Integrability in Out of Equilibrium Systems’." Journal of Statistical Mechanics: Theory and Experiment 2016, no. 6 (June 27, 2016): 064001. http://dx.doi.org/10.1088/1742-5468/2016/06/064001.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Cugliandolo, Leticia F. "Out-of-equilibrium dynamics of classical and quantum complex systems." Comptes Rendus Physique 14, no. 8 (October 2013): 685–99. http://dx.doi.org/10.1016/j.crhy.2013.09.004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Bandyopadhyay, Souvik, Sourav Bhattacharjee, and Diptiman Sen. "Driven quantum many-body systems and out-of-equilibrium topology." Journal of Physics: Condensed Matter 33, no. 39 (July 22, 2021): 393001. http://dx.doi.org/10.1088/1361-648x/ac1151.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Khatami, Ehsan, Guido Pupillo, Mark Srednicki, and Marcos Rigol. "Fluctuation-dissipation theorem in isolated quantum systems out of equilibrium." Journal of Physics: Conference Series 510 (May 15, 2014): 012035. http://dx.doi.org/10.1088/1742-6596/510/1/012035.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Acevedo, O. L., L. Quiroga, F. J. Rodríguez, and N. F. Johnson. "Robust quantum correlations in out-of-equilibrium matter–light systems." New Journal of Physics 17, no. 9 (September 9, 2015): 093005. http://dx.doi.org/10.1088/1367-2630/17/9/093005.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Hubeny, Veronika E., and Mukund Rangamani. "A Holographic View on Physics out of Equilibrium." Advances in High Energy Physics 2010 (2010): 1–84. http://dx.doi.org/10.1155/2010/297916.

Full text

Abstract:

We review the recent developments in applying holographic methods to understand nonequilibrium physics in strongly coupled field theories. The emphasis will be on elucidating the relation between evolution of quantum field theories perturbed away from equilibrium and the dual picture of dynamics of classical fields in black hole backgrounds. In particular, we discuss the linear response regime, the hydrodynamic regime, and finally the nonlinear regime of interacting quantum systems. We also describe how the duality might be used to learn some salient aspects of black hole physics in terms of field theory observables.

APA, Harvard, Vancouver, ISO, and other styles

11

Carollo, Angelo, Bernardo Spagnolo, and Davide Valenti. "Non-Equilibrium Phenomena in Quantum Systems, Criticality and Metastability." Proceedings 12, no. 1 (September 29, 2019): 43. http://dx.doi.org/10.3390/proceedings2019012043.

Full text

Abstract:

We summarise here some relevant results related to non-equilibrium quantum systems. We characterise quantum phase transitions (QPT) in out-of-equilibrium quantum systems through a novel approach based on geometrical and topological properties of mixed quantum systems. We briefly describe results related to non-perturbative studies of the bistable dynamics of a quantum particle coupled to an environment. Finally, we shortly summarise recent studies on the generation of solitons in current-biased long Josephson junctions.

APA, Harvard, Vancouver, ISO, and other styles

12

Venuti, Lorenzo Campos, and Paolo Zanardi. "Theory of temporal fluctuations in isolated quantum systems." International Journal of Modern Physics B 29, no. 14 (May 22, 2015): 1530008. http://dx.doi.org/10.1142/s021797921530008x.

Full text

Abstract:

When an isolated quantum system is driven out of equilibrium, expectation values of general observables start oscillating in time. This paper reviews the general theory of such temporal fluctuations. We first survey some results on the strength of such temporal fluctuations. For example temporal fluctuations are exponentially small in the system's volume for generic systems whereas they fall-off algebraically in integrable systems. We then concentrate on the so-called quench scenario where the system is driven out-of-equilibrium under the application of a sudden perturbation. For sufficiently small perturbations, temporal fluctuations of physical observables can be characterized in full generality and can be used as an effective tool to probe quantum criticality of the underlying model. In the off-critical region the distribution becomes Gaussian. Close to criticality the distribution becomes a universal function uniquely characterized by a single critical exponent, that we compute explicitly. This contrasts standard equilibrium quantum fluctuations for which the critical distribution depends on a numerable set of critical coefficients and is known only for limited examples. The possibility of using temporal fluctuations to determine pseudo-critical boundaries in optical lattice experiments is further reviewed.

APA, Harvard, Vancouver, ISO, and other styles

13

Aschbacher, Walter H. "A Rigorous Scattering Approach to Quasifree Fermionic Systems out of Equilibrium." Journal of Non-Equilibrium Thermodynamics 44, no. 3 (July 26, 2019): 261–75. http://dx.doi.org/10.1515/jnet-2018-0071.

Full text

Abstract:

Abstract Within the rigorous axiomatic framework for the description of quantum mechanical systems with a large number of degrees of freedom, we construct the so-called nonequilibrium steady state for the quasifree fermionic system corresponding to the isotropic XY chain in which a finite sample, subject to a local gauge breaking anisotropy perturbation, is coupled to two thermal reservoirs at different temperatures. Using time dependent and stationary scattering theory, we rigorously prove, from first principles, that the nonequilibrium system under consideration is thermodynamically nontrivial, i. e., that its entropy production rate is strictly positive.

APA, Harvard, Vancouver, ISO, and other styles

14

Kennett, Malcolm P. "Out-of-Equilibrium Dynamics of the Bose-Hubbard Model." ISRN Condensed Matter Physics 2013 (June 12, 2013): 1–39. http://dx.doi.org/10.1155/2013/393616.

Full text

Abstract:

The Bose-Hubbard model is the simplest model of interacting bosons on a lattice. It has recently been the focus of much attention due to the realization of this model with cold atoms in an optical lattice. The ability to tune parameters in the Hamiltonian as a function of time in cold atom systems has opened up the possibility of studying out-of-equilibrium dynamics, including crossing the quantum critical region of the model in a controlled way. In this paper, I give a brief introduction to the Bose Hubbard model, and its experimental realization and then give an account of theoretical and experimental efforts to understand out-of-equilibrium dynamics in this model, focusing on quantum quenches, both instantaneous and of finite duration. I discuss slow dynamics that have been observed theoretically and experimentally for some quenches from the superfluid phase to the Mott insulating phase and the picture of two timescales, one for fast local equilibration and another for slow global equilibration, that appears to characterize this situation. I also discuss the theoretical and experimental observation of the Lieb-Robinson bounds for a variety of quenches and the Kibble-Zurek mechanism in quenches from the Mott insulator to superfluid. I conclude with a discussion of open questions and future directions.

APA, Harvard, Vancouver, ISO, and other styles

15

Ageev, Dmitry. "Holography, quantum complexity and quantum chaos in different models." EPJ Web of Conferences 191 (2018): 06006. http://dx.doi.org/10.1051/epjconf/201819106006.

Full text

Abstract:

This contribution to Quarks’2018 conference proceedings is based on the talk presenting papers [1, 2] at the conference. These papers are devoted to the holographic description of chaos and quantum complexity in the strongly interacting systems out of equilibrium. In the first part of the talk we present different holographic complexity proposals in out-of-equilibrium CFT following the local perturbation. The second part is devoted to the chaotic growth of the local operator at a finite chemical potential. There are numerous results stating that the chemical potential may lead to the chaos disappearance, and we confirm the results from holography.

APA, Harvard, Vancouver, ISO, and other styles

16

Medel-Portugal, Carlos, Juan Manuel Solano-Altamirano, and José Luis E. Carrillo-Estrada. "Classical and Quantum H-Theorem Revisited: Variational Entropy and Relaxation Processes." Entropy 23, no. 3 (March 19, 2021): 366. http://dx.doi.org/10.3390/e23030366.

Full text

Abstract:

We propose a novel framework to describe the time-evolution of dilute classical and quantum gases, initially out of equilibrium and with spatial inhomogeneities, towards equilibrium. Briefly, we divide the system into small cells and consider the local equilibrium hypothesis. We subsequently define a global functional that is the sum of cell H-functionals. Each cell functional recovers the corresponding Maxwell–Boltzmann, Fermi–Dirac, or Bose–Einstein distribution function, depending on the classical or quantum nature of the gas. The time-evolution of the system is described by the relationship dH/dt≤0, and the equality condition occurs if the system is in the equilibrium state. Via the variational method, proof of the previous relationship, which might be an extension of the H-theorem for inhomogeneous systems, is presented for both classical and quantum gases. Furthermore, the H-functionals are in agreement with the correspondence principle. We discuss how the H-functionals can be identified with the system’s entropy and analyze the relaxation processes of out-of-equilibrium systems.

APA, Harvard, Vancouver, ISO, and other styles

17

Esfarjani, Keivan, and Yuan Liang. "Equilibrium and Non-Equilibrium Lattice Dynamics of Anharmonic Systems." Entropy 24, no. 11 (November 1, 2022): 1585. http://dx.doi.org/10.3390/e24111585.

Full text

Abstract:

In this review, motivated by the recent interest in high-temperature materials, we review our recent progress in theories of lattice dynamics in and out of equilibrium. To investigate thermodynamic properties of anharmonic crystals, the self-consistent phonon theory was developed, mainly in the 1960s, for rare gas atoms and quantum crystals. We have extended this theory to investigate the properties of the equilibrium state of a crystal, including its unit cell shape and size, atomic positions and lattice dynamical properties. Using the equation-of-motion method combined with the fluctuation–dissipation theorem and the Donsker–Furutsu–Novikov (DFN) theorem, this approach was also extended to investigate the non-equilibrium case where there is heat flow across a junction or an interface. The formalism is a classical one and therefore valid at high temperatures.

APA, Harvard, Vancouver, ISO, and other styles

18

Campi, Gaetano, and Antonio Bianconi. "Evolution of Complexity in Out-of-Equilibrium Systems by Time-Resolved or Space-Resolved Synchrotron Radiation Techniques." Condensed Matter 4, no. 1 (March 14, 2019): 32. http://dx.doi.org/10.3390/condmat4010032.

Full text

Abstract:

Out-of-equilibrium phenomena are attracting high interest in physics, materials science, chemistry and life sciences. In this state, the study of structural fluctuations at different length scales in time and space are necessary to achieve significant advances in the understanding of the structure-functionality relationship. The visualization of patterns arising from spatiotemporal fluctuations is nowadays possible thanks to new advances in X-ray instrumentation development that combine high-resolution both in space and in time. We present novel experimental approaches using high brilliance synchrotron radiation sources, fast detectors and focusing optics, joint with advanced data analysis based on automated statistical, mathematical and imaging processing tools. This approach has been used to investigate structural fluctuations in out-of-equilibrium systems in the novel field of inhomogeneous quantum complex matter at the crossing point of technology, physics and biology. In particular, we discuss how nanoscale complexity controls the emergence of high-temperature superconductivity (HTS), myelin functionality and formation of hybrid organic-inorganic supramolecular assembly. The emergent complex geometries, opening novel venues to quantum technology and to the development of quantum physics of living systems, are discussed.

APA, Harvard, Vancouver, ISO, and other styles

19

Mi, Xiao, Matteo Ippoliti, Chris Quintana, Ami Greene, Zijun Chen, Jonathan Gross, Frank Arute, et al. "Time-crystalline eigenstate order on a quantum processor." Nature 601, no. 7894 (November 30, 2021): 531–36. http://dx.doi.org/10.1038/s41586-021-04257-w.

Full text

Abstract:

AbstractQuantum many-body systems display rich phase structure in their low-temperature equilibrium states1. However, much of nature is not in thermal equilibrium. Remarkably, it was recently predicted that out-of-equilibrium systems can exhibit novel dynamical phases2–8 that may otherwise be forbidden by equilibrium thermodynamics, a paradigmatic example being the discrete time crystal (DTC)7,9–15. Concretely, dynamical phases can be defined in periodically driven many-body-localized (MBL) systems via the concept of eigenstate order7,16,17. In eigenstate-ordered MBL phases, the entire many-body spectrum exhibits quantum correlations and long-range order, with characteristic signatures in late-time dynamics from all initial states. It is, however, challenging to experimentally distinguish such stable phases from transient phenomena, or from regimes in which the dynamics of a few select states can mask typical behaviour. Here we implement tunable controlled-phase (CPHASE) gates on an array of superconducting qubits to experimentally observe an MBL-DTC and demonstrate its characteristic spatiotemporal response for generic initial states7,9,10. Our work employs a time-reversal protocol to quantify the impact of external decoherence, and leverages quantum typicality to circumvent the exponential cost of densely sampling the eigenspectrum. Furthermore, we locate the phase transition out of the DTC with an experimental finite-size analysis. These results establish a scalable approach to studying non-equilibrium phases of matter on quantum processors.

APA, Harvard, Vancouver, ISO, and other styles

20

Minganti, Fabrizio, Ievgen I. Arkhipov, Adam Miranowicz, and Franco Nori. "Continuous dissipative phase transitions with or without symmetry breaking." New Journal of Physics 23, no. 12 (December 1, 2021): 122001. http://dx.doi.org/10.1088/1367-2630/ac3db8.

Full text

Abstract:

Abstract The paradigm of second-order phase transitions (PTs) induced by spontaneous symmetry breaking (SSB) in thermal and quantum systems is a pillar of modern physics that has been fruitfully applied to out-of-equilibrium open quantum systems. Dissipative phase transitions (DPTs) of second order are often connected with SSB, in close analogy with well-known thermal second-order PTs in closed quantum and classical systems. That is, a second-order DPT should disappear by preventing the occurrence of SSB. Here, we prove this statement to be wrong, showing that, surprisingly, SSB is not a necessary condition for the occurrence of second-order DPTs in out-of-equilibrium open quantum systems. We analytically prove this result using the Liouvillian theory of DPTs, and demonstrate this anomalous transition in a paradigmatic laser model, where we can arbitrarily remove SSB while retaining criticality, and on a Z 2-symmetric model of a two-photon Kerr resonator. This new type of PT cannot be interpreted as a ‘semiclassical’ bifurcation, because, after the DPT, the system steady state remains unique.

APA, Harvard, Vancouver, ISO, and other styles

21

Coppola, M., and D. Karevski. "Some speculations about local thermalization of nonequilibrium extended quantum systems." Condensed Matter Physics 26, no. 1 (2023): 13502. http://dx.doi.org/10.5488/cmp.26.13502.

Full text

Abstract:

We discuss the possibility of defining an emergent local temperature in extended quantum many-body systems evolving out of equilibrium. For the most simple case of free-fermionic systems, we give an explicit formula for the effective temperature in the case of, not necessarily unitary, Gaussian preserving dynamics. In this framework, we consider the hopping fermions on a one-dimensional lattice submitted to randomly distributed projective measurements of the local occupation numbers. We show from the average over many quantum trajectories that the effective temperature relaxes exponentially towards infinity.

APA, Harvard, Vancouver, ISO, and other styles

22

Zhang, Xu, Wenjie Jiang, Jinfeng Deng, Ke Wang, Jiachen Chen, Pengfei Zhang, Wenhui Ren, et al. "Digital quantum simulation of Floquet symmetry-protected topological phases." Nature 607, no. 7919 (July 20, 2022): 468–73. http://dx.doi.org/10.1038/s41586-022-04854-3.

Full text

Abstract:

AbstractQuantum many-body systems away from equilibrium host a rich variety of exotic phenomena that are forbidden by equilibrium thermodynamics. A prominent example is that of discrete time crystals1–8, in which time-translational symmetry is spontaneously broken in periodically driven systems. Pioneering experiments have observed signatures of time crystalline phases with trapped ions9,10, solid-state spin systems11–15, ultracold atoms16,17 and superconducting qubits18–20. Here we report the observation of a distinct type of non-equilibrium state of matter, Floquet symmetry-protected topological phases, which are implemented through digital quantum simulation with an array of programmable superconducting qubits. We observe robust long-lived temporal correlations and subharmonic temporal response for the edge spins over up to 40 driving cycles using a circuit of depth exceeding 240 and acting on 26 qubits. We demonstrate that the subharmonic response is independent of the initial state, and experimentally map out a phase boundary between the Floquet symmetry-protected topological and thermal phases. Our results establish a versatile digital simulation approach to exploring exotic non-equilibrium phases of matter with current noisy intermediate-scale quantum processors21.

APA, Harvard, Vancouver, ISO, and other styles

23

Hong, Jongbae. "Nonlinear entangled quantum dynamics in many-body systems with strong electron correlation." International Journal of Modern Physics B 31, no. 10 (April 20, 2017): 1742009. http://dx.doi.org/10.1142/s0217979217420097.

Full text

Abstract:

A quantum impurity system out of equilibrium comprises two metallic reservoirs with different chemical potentials and one mediating spin impurity between them. We study the highly nonlinear tunneling conductance of this system, and clarify that three coherent peaks, one zero-bias peak and two side peaks, naturally appear in the tunneling conductance. We use the Liouvillian approach, in which a complete set of basis operators is available, and construct a Liouville matrix to obtain Green’s function at the mediating site. We show that the two coherent side peaks are the outcome of steady-state nonequilibrium combined with strong electron correlation at the mediating site. Tunneling in the quantum impurity system out of equilibrium is performed by an entangled state which is a linear combination of two Kondo singlets formed by the spin at the mediating site and the coherent spins in each reservoir. The fluctuation by incoherent spins is also included. The spectral weights and positions of the three coherent peaks are analytically discussed via atomic limit analysis. Our theoretical results well fit experimental data obtained for quantum point contacts with symmetric and asymmetric Kondo couplings.

APA, Harvard, Vancouver, ISO, and other styles

24

Holmes, Zoe, Gopikrishnan Muraleedharan, Rolando D. Somma, Yigit Subasi, and Burak Şahinoğlu. "Quantum algorithms from fluctuation theorems: Thermal-state preparation." Quantum 6 (October 6, 2022): 825. http://dx.doi.org/10.22331/q-2022-10-06-825.

Full text

Abstract:

Fluctuation theorems provide a correspondence between properties of quantum systems in thermal equilibrium and a work distribution arising in a non-equilibrium process that connects two quantum systems with Hamiltonians H0 and H1=H0+V. Building upon these theorems, we present a quantum algorithm to prepare a purification of the thermal state of H1 at inverse temperature β≥0 starting from a purification of the thermal state of H0. The complexity of the quantum algorithm, given by the number of uses of certain unitaries, is O~(eβ(ΔA−wl)/2), where ΔA is the free-energy difference between H1 and H0, and wl is a work cutoff that depends on the properties of the work distribution and the approximation error ϵ>0. If the non-equilibrium process is trivial, this complexity is exponential in β‖V‖, where ‖V‖ is the spectral norm of V. This represents a significant improvement of prior quantum algorithms that have complexity exponential in β‖H1‖ in the regime where ‖V‖≪‖H1‖. The dependence of the complexity in ϵ varies according to the structure of the quantum systems. It can be exponential in 1/ϵ in general, but we show it to be sublinear in 1/ϵ if H0 and H1 commute, or polynomial in 1/ϵ if H0 and H1 are local spin systems. The possibility of applying a unitary that drives the system out of equilibrium allows one to increase the value of wl and improve the complexity even further. To this end, we analyze the complexity for preparing the thermal state of the transverse field Ising model using different non-equilibrium unitary processes and see significant complexity improvements.

APA, Harvard, Vancouver, ISO, and other styles

25

Dutta, Amit, and Krishnendu Sengupta. "Quantum dynamics research in India: a perspective." Journal of Physics: Condensed Matter 34, no. 10 (December 22, 2021): 100401. http://dx.doi.org/10.1088/1361-648x/ac410a.

Full text

Abstract:

Abstract Comprehending out-of-equilibrium properties of quantum many-body systems is still an emergent area of recent research. The upsurge in this area is motivated by tremendous progress in experimental studies, the key platforms being ultracold atoms and trapped ion systems. There has been a significant contribution from India to this vibrant field. This special issue which includes both review articles and original research papers highlights some of these contributions.

APA, Harvard, Vancouver, ISO, and other styles

26

Moore, Joel E. "A perspective on quantum integrability in many-body-localized and Yang–Baxter systems." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2108 (October 30, 2017): 20160429. http://dx.doi.org/10.1098/rsta.2016.0429.

Full text

Abstract:

Two of the most active areas in quantum many-particle dynamics involve systems with an unusually large number of conservation laws. Many-body-localized systems generalize ideas of Anderson localization by disorder to interacting systems. While localization still exists with interactions and inhibits thermalization, the interactions between conserved quantities lead to some dramatic differences from the Anderson case. Quantum integrable models such as the XXZ spin chain or Bose gas with delta-function interactions also have infinite sets of conservation laws, again leading to modifications of conventional thermalization. A practical way to treat the hydrodynamic evolution from local equilibrium to global equilibrium in such models is discussed. This paper expands upon a presentation at a discussion meeting of the Royal Society on 7 February 2017. The work described was carried out with a number of collaborators, including Jens Bardarson, Vir Bulchandani, Roni Ilan, Christoph Karrasch, Siddharth Parameswaran, Frank Pollmann and Romain Vasseur. This article is part of the themed issue ‘Breakdown of ergodicity in quantum systems: from solids to synthetic matter’.

APA, Harvard, Vancouver, ISO, and other styles

27

Bonitz, M., S. Hermanns, K. Kobusch, and K. Balzer. "Nonequilibrium Green function approach to the pair distribution function of quantum many-body systems out of equilibrium." Journal of Physics: Conference Series 427 (March 27, 2013): 012002. http://dx.doi.org/10.1088/1742-6596/427/1/012002.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Apollaro, Tony J. G., and Salvatore Lorenzo. "Coexistence of Different Scaling Laws for the Entanglement Entropy in a Periodically Driven System." Proceedings 12, no. 1 (June 25, 2019): 6. http://dx.doi.org/10.3390/proceedings2019012006.

Full text

Abstract:

The out-of-equilibrium dynamics of many body systems has recently received a burst of interest, also due to experimental implementations. The dynamics of observables, such as magnetization and susceptibilities, and quantum information related quantities, such as concurrence and entanglement entropy, have been investigated under different protocols bringing the system out of equilibrium. In this paper we focus on the entanglement entropy dynamics under a sinusoidal drive of the tranverse magnetic field in the 1D quantum Ising model. We find that the area and the volume law of the entanglement entropy coexist under periodic drive for an initial non-critical ground state. Furthermore, starting from a critical ground state, the entanglement entropy exhibits finite size scaling even under such a periodic drive. This critical-like behaviour of the out-of-equilibrium driven state can persist for arbitrarily long time, provided that the entanglement entropy is evaluated on increasingly subsytem sizes, whereas for smaller sizes a volume law holds. Finally, we give an interpretation of the simultaneous occurrence of critical and non-critical behaviour in terms of the propagation of Floquet quasi-particles.

APA, Harvard, Vancouver, ISO, and other styles

29

Rodríguez, Antonio, Alessandro Pluchino, Ugur Tirnakli, Andrea Rapisarda, and Constantino Tsallis. "Nonextensive Footprints in Dissipative and Conservative Dynamical Systems." Symmetry 15, no. 2 (February 7, 2023): 444. http://dx.doi.org/10.3390/sym15020444.

Full text

Abstract:

Despite its centennial successes in describing physical systems at thermal equilibrium, Boltzmann–Gibbs (BG) statistical mechanics have exhibited, in the last several decades, several flaws in addressing out-of-equilibrium dynamics of many nonlinear complex systems. In such circumstances, it has been shown that an appropriate generalization of the BG theory, known as nonextensive statistical mechanics and based on nonadditive entropies, is able to satisfactorily handle wide classes of anomalous emerging features and violations of standard equilibrium prescriptions, such as ergodicity, mixing, breakdown of the symmetry of homogeneous occupancy of phase space, and related features. In the present study, we review various important results of nonextensive statistical mechanics for dissipative and conservative dynamical systems. In particular, we discuss applications to both discrete-time systems with a few degrees of freedom and continuous-time ones with many degrees of freedom, as well as to asymptotically scale-free networks and systems with diverse dimensionalities and ranges of interactions, of either classical or quantum nature.

APA, Harvard, Vancouver, ISO, and other styles

30

Gulian, Armen, Rajendra Dulal, Serafim Teknowijoyo, and Sara Chahid. "Dialogue on a superconducting laser operating via nonequilibrium inversed population." Modern Physics Letters B 34, no. 22 (June 30, 2020): 2030005. http://dx.doi.org/10.1142/s0217984920300057.

Full text

Abstract:

In nonequilibrium states, the entropy is reduced from its maximum thermodynamic equilibrium value by virtue of an external energy supply. Such states are characterized by a higher ordering compared to the equilibrium. Human beings represent the highest level of nonequilibrium state, at least in the known part of the Universe. Other physical systems are also well-known, for example, quantum generators, e.g., lasers. Their operation requires a high level of deviation from equilibrium called inverse population. In turn, states out of equilibrium require energy influx for their maintenance, i.e., they should be open systems. In this short review we describe in the form of dialogue between Prof. A. M. Gulian and his younger colleagues Dr. Rajendra Dulal, Dr. Serafim Teknowijoyo and Dr. Sara Chahid the task of achieving inverse population in superconductors. Then, the dialogue moves towards experimental consequences that nonequilibrium superconductors can yield. These include topics related with deeper understanding of mechanisms of superconductivity in novel materials, in particular related to the “glue” which pairs electrons in Cooper pairs. Such understanding will facilitate development of Bose-field quantum generators like lasers, and coherent acoustic as well as paramagnon quantum sources, none of which are yet realized in nonequilibrium superconductors.

APA, Harvard, Vancouver, ISO, and other styles

31

Nessi, N., and A. Iucci. "Equations of Motion for the Out-of-Equilibrium Dynamics of Isolated Quantum Systems from the Projection Operator Technique." Journal of Physics: Conference Series 568, no. 1 (December 8, 2014): 012013. http://dx.doi.org/10.1088/1742-6596/568/1/012013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Khan, S. A., Z. Iqbal, and Z. Wazir. "Quantum Ion-Acoustic Oscillations in Single-Walled Carbon Nanotubes." Zeitschrift für Naturforschung A 71, no. 5 (May 1, 2016): 397–404. http://dx.doi.org/10.1515/zna-2015-0391.

Full text

Abstract:

AbstractQuantum ion-acoustic oscillations in single-walled carbon nanotubes are studied by employing a quantum hydrodynamics model. The dispersion equation is obtained by Fourier transformation, which exhibits the existence of quantum ion-acoustic wave affected by change of density balance due to presence of positive or negative heavy species as stationary ion clusters and wave potential at equilibrium. The numerical results are presented, and the role of quantum degeneracy, nanotube geometry, electron exchange-correlation effects, and concentration and polarity of heavy species on wave dispersion is pointed out for typical systems of interest.

APA, Harvard, Vancouver, ISO, and other styles

33

Sagawa, Takahiro, Philippe Faist, Kohtaro Kato, Keiji Matsumoto, Hiroshi Nagaoka, and Fernando G. S. L. Brandão. "Asymptotic reversibility of thermal operations for interacting quantum spin systems via generalized quantum Stein’s lemma." Journal of Physics A: Mathematical and Theoretical 54, no. 49 (November 19, 2021): 495303. http://dx.doi.org/10.1088/1751-8121/ac333c.

Full text

Abstract:

Abstract For quantum spin systems in any spatial dimension with a local, translation-invariant Hamiltonian, we prove that asymptotic state convertibility from a quantum state to another one by a thermodynamically feasible class of quantum dynamics, called thermal operations, is completely characterized by the Kullback–Leibler (KL) divergence rate, if the state is translation-invariant and spatially ergodic. Our proof consists of two parts and is phrased in terms of a branch of the quantum information theory called the resource theory. First, we prove that any states, for which the min and max Rényi divergences collapse approximately to a single value, can be approximately reversibly converted into one another by thermal operations with the aid of a small source of quantum coherence. Second, we prove that these divergences collapse asymptotically to the KL divergence rate for any translation-invariant ergodic state. We show this via a generalization of the quantum Stein’s lemma for quantum hypothesis testing beyond independent and identically distributed situations. Our result implies that the KL divergence rate serves as a thermodynamic potential that provides a complete characterization of thermodynamic convertibility of ergodic states of quantum many-body systems in the thermodynamic limit, including out-of-equilibrium and fully quantum situations.

APA, Harvard, Vancouver, ISO, and other styles

34

Bode, Niels, Silvia Viola Kusminskiy, Reinhold Egger, and Felix von Oppen. "Current-induced forces in mesoscopic systems: A scattering-matrix approach." Beilstein Journal of Nanotechnology 3 (February 20, 2012): 144–62. http://dx.doi.org/10.3762/bjnano.3.15.

Full text

Abstract:

Nanoelectromechanical systems are characterized by an intimate connection between electronic and mechanical degrees of freedom. Due to the nanoscopic scale, current flowing through the system noticeably impacts upons the vibrational dynamics of the device, complementing the effect of the vibrational modes on the electronic dynamics. We employ the scattering-matrix approach to quantum transport in order to develop a unified theory of nanoelectromechanical systems out of equilibrium. For a slow mechanical mode the current can be obtained from the Landauer–Büttiker formula in the strictly adiabatic limit. The leading correction to the adiabatic limit reduces to Brouwer’s formula for the current of a quantum pump in the absence of a bias voltage. The principal results of the present paper are the scattering-matrix expressions for the current-induced forces acting on the mechanical degrees of freedom. These forces control the Langevin dynamics of the mechanical modes. Specifically, we derive expressions for the (typically nonconservative) mean force, for the (possibly negative) damping force, an effective “Lorentz” force that exists even for time-reversal-invariant systems, and the fluctuating Langevin force originating from Nyquist and shot noise of the current flow. We apply our general formalism to several simple models that illustrate the peculiar nature of the current-induced forces. Specifically, we find that in out-of-equilibrium situations the current-induced forces can destabilize the mechanical vibrations and cause limit-cycle dynamics.

APA, Harvard, Vancouver, ISO, and other styles

35

Goihl, Marcel, Mathis Friesdorf, Albert H. Werner, Winton Brown, and Jens Eisert. "Experimentally Accessible Witnesses of Many-Body Localization." Quantum Reports 1, no. 1 (June 17, 2019): 50–62. http://dx.doi.org/10.3390/quantum1010006.

Full text

Abstract:

The phenomenon of many-body localized (MBL) systems has attracted significant interest in recent years, for its intriguing implications from a perspective of both condensed-matter and statistical physics: they are insulators even at non-zero temperature and fail to thermalize, violating expectations from quantum statistical mechanics. What is more, recent seminal experimental developments with ultra-cold atoms in optical lattices constituting analog quantum simulators have pushed many-body localized systems into the realm of physical systems that can be measured with high accuracy. In this work, we introduce experimentally accessible witnesses that directly probe distinct features of MBL, distinguishing it from its Anderson counterpart. We insist on building our toolbox from techniques available in the laboratory, including on-site addressing, super-lattices, and time-of-flight measurements, identifying witnesses based on fluctuations, density–density correlators, densities, and entanglement. We build upon the theory of out of equilibrium quantum systems, in conjunction with tensor network and exact simulations, showing the effectiveness of the tools for realistic models.

APA, Harvard, Vancouver, ISO, and other styles

36

Markmann, Sergej, Martin Franckié, Shovon Pal, David Stark, Mattias Beck, Manfred Fiebig, Giacomo Scalari, and Jérôme Faist. "Two-dimensional spectroscopy on a THz quantum cascade structure." Nanophotonics 10, no. 1 (October 14, 2020): 171–80. http://dx.doi.org/10.1515/nanoph-2020-0369.

Full text

Abstract:

AbstractUnderstanding and controlling the nonlinear optical properties and coherent quantum evolution of complex multilevel systems out of equilibrium is essential for the new semiconductor device generation. In this work, we investigate the nonlinear system properties of an unbiased quantum cascade structure by performing two-dimensional THz spectroscopy. We study the time-resolved coherent quantum evolution after it is driven far from equilibrium by strong THz pulses and demonstrate the existence of multiple nonlinear signals originating from the engineered subbands and find the lifetimes of those states to be in the order of 4–8 ps. Moreover, we observe a coherent population exchange among the first four intersubband levels during the relaxation, which have been confirmed with our simulation. We model the experimental results with a time-resolved density matrix based on the master equation in Lindblad form, including both coherent and incoherent transitions between all density matrix elements. This allows us to replicate qualitatively the experimental observations and provides access to their microscopic origin.

APA, Harvard, Vancouver, ISO, and other styles

37

Carabba, Nicoletta, Niklas Hörnedal, and Adolfo del Campo. "Quantum speed limits on operator flows and correlation functions." Quantum 6 (December 22, 2022): 884. http://dx.doi.org/10.22331/q-2022-12-22-884.

Full text

Abstract:

Quantum speed limits (QSLs) identify fundamental time scales of physical processes by providing lower bounds on the rate of change of a quantum state or the expectation value of an observable. We introduce a generalization of QSL for unitary operator flows, which are ubiquitous in physics and relevant for applications in both the quantum and classical domains. We derive two types of QSLs and assess the existence of a crossover between them, that we illustrate with a qubit and a random matrix Hamiltonian, as canonical examples. We further apply our results to the time evolution of autocorrelation functions, obtaining computable constraints on the linear dynamical response of quantum systems out of equilibrium and the quantum Fisher information governing the precision in quantum parameter estimation.

APA, Harvard, Vancouver, ISO, and other styles

38

UMEZAWA, H., and Y. YAMANAKA. "TEMPORAL DESCRIPTION OF THERMAL QUANTUM FIELDS." Modern Physics Letters A 07, no. 37 (December 7, 1992): 3509–20. http://dx.doi.org/10.1142/s0217732392002925.

Full text

Abstract:

By making use of time-dependent Bogoliubov transformations, we develop a calculation technique for time-dependent non-equilibrium systems of quantum fields in a time-representation (t-representation). The corrected one-body propagator in the t-representation turns out to have the form B−1 (diagonal matrix) B (B being a thermal Bogoliubov matrix). Applying the usual on-shell concept to the diagonal matrix part of the self-energy, we formulate a self-consistent renormalization scheme. This renormalization determines the vacuum and leads to a kinetic equation for the number density parameter, which reduces to the Boltzmann equation in the lowest approximation. This gives us the increasing entropy in time (the second law of thermodynamics).

APA, Harvard, Vancouver, ISO, and other styles

39

Madeira, Lucas, and Vanderlei S. Bagnato. "Non-Thermal Fixed Points in Bose Gas Experiments." Symmetry 14, no. 4 (March 25, 2022): 678. http://dx.doi.org/10.3390/sym14040678.

Full text

Abstract:

One of the most challenging tasks in physics has been understanding the route an out-of-equilibrium system takes to its thermalized state. This problem can be particularly overwhelming when one considers a many-body quantum system. However, several recent theoretical and experimental studies have indicated that some far-from-equilibrium systems display universal dynamics when close to a so-called non-thermal fixed point (NTFP), following a rescaling of both space and time. This opens up the possibility of a general framework for studying and categorizing out-of-equilibrium phenomena into well-defined universality classes. This paper reviews the recent advances in observing NTFPs in experiments involving Bose gases. We provide a brief introduction to the theory behind this universal scaling, focusing on experimental observations of NTFPs. We present the benefits of NTFP universality classes by analogy with renormalization group theory in equilibrium critical phenomena.

APA, Harvard, Vancouver, ISO, and other styles

40

Wei, Di S., Toeno van der Sar, Seung Hwan Lee, Kenji Watanabe, Takashi Taniguchi, Bertrand I. Halperin, and Amir Yacoby. "Electrical generation and detection of spin waves in a quantum Hall ferromagnet." Science 362, no. 6411 (October 11, 2018): 229–33. http://dx.doi.org/10.1126/science.aar4061.

Full text

Abstract:

Spin waves are collective excitations of magnetic systems. An attractive setting for studying long-lived spin-wave physics is the quantum Hall (QH) ferromagnet, which forms spontaneously in clean two-dimensional electron systems at low temperature and in a perpendicular magnetic field. We used out-of-equilibrium occupation of QH edge channels in graphene to excite and detect spin waves in magnetically ordered QH states. Our experiments provide direct evidence for long-distance spin-wave propagation through different ferromagnetic phases in the N = 0 Landau level, as well as across the insulating canted antiferromagnetic phase. Our results will enable experimental investigation of the fundamental magnetic properties of these exotic two-dimensional electron systems.

APA, Harvard, Vancouver, ISO, and other styles

41

Bernard, Denis, and Tony Jin. "Solution to the Quantum Symmetric Simple Exclusion Process: The Continuous Case." Communications in Mathematical Physics 384, no. 2 (April 21, 2021): 1141–85. http://dx.doi.org/10.1007/s00220-021-04087-x.

Full text

Abstract:

AbstractThe quantum symmetric simple exclusion process (Q-SSEP) is a model for quantum stochastic dynamics of fermions hopping along the edges of a graph with Brownian noisy amplitudes and driven out-of-equilibrium by injection-extraction processes at a few vertices. We present a solution for the invariant probability measure of the one dimensional Q-SSEP in the infinite size limit by constructing the steady correlation functions of the system density matrix and quantum expectation values. These correlation functions code for a rich structure of fluctuating quantum correlations and coherences. Although our construction does not rely on the standard techniques from the theory of integrable systems, it is based on a remarkable interplay between the permutation groups and polynomials. We incidentally point out a possible combinatorial interpretation of the Q-SSEP correlation functions via a surprising connexion with geometric combinatorics and the associahedron polytopes.

APA, Harvard, Vancouver, ISO, and other styles

42

Smale, Scott, Peiru He, Ben A. Olsen, Kenneth G. Jackson, Haille Sharum, Stefan Trotzky, Jamir Marino, Ana Maria Rey, and Joseph H. Thywissen. "Observation of a transition between dynamical phases in a quantum degenerate Fermi gas." Science Advances 5, no. 8 (August 2019): eaax1568. http://dx.doi.org/10.1126/sciadv.aax1568.

Full text

Abstract:

A proposed paradigm for out-of-equilibrium quantum systems is that an analog of quantum phase transitions exists between parameter regimes of qualitatively distinct time-dependent behavior. Here, we present evidence of such a transition between dynamical phases in a cold-atom quantum simulator of the collective Heisenberg model. Our simulator encodes spin in the hyperfine states of ultracold fermionic potassium. Atoms are pinned in a network of single-particle modes, whose spatial extent emulates the long-range interactions of traditional quantum magnets. We find that below a critical interaction strength, magnetization of an initially polarized fermionic gas decays quickly, while above the transition point, the magnetization becomes long-lived because of an energy gap that protects against dephasing by the inhomogeneous axial field. Our quantum simulation reveals a nonequilibrium transition predicted to exist but not yet directly observed in quenched s-wave superconductors.

APA, Harvard, Vancouver, ISO, and other styles

43

GUSEINOV, N. M., K. A. RUSTAMOV, and S. M. SEYID-RZAYEVA. "THE POLARON EFFECTS AND RELAXATION OF NON-EQUILIBRIUM ELECTRONS IN THE QUASI-TWO-DIMENSIONAL SYSTEMS." Modern Physics Letters B 05, no. 02 (January 20, 1991): 139–49. http://dx.doi.org/10.1142/s0217984991000186.

Full text

Abstract:

The problem on weak-coupling polaron in the quasi-two-dimensional electron system is solved. Analytical expressions for polaron energy shift of the subband and polaron contribution to the effective electron mass with arbitrary quantum well width are found. The expressions obtained give the well-known values for two- and three-dimensional limiting cases. A comparison of the polaron contribution to the mass with the available experimental data is carried out. Energy relaxation processes of non-equilibrium quasi-two-dimensional electrons with the optic phonon emission are also considered. General analytical expressions for the frequencies of intra-subband and inter-subband transitions for the threshold electron energy are obtained.

APA, Harvard, Vancouver, ISO, and other styles

44

Aris Chatzidimitriou-Dreismann, C. "Quantumness of correlations in nanomaterials—experimental evidence and unconventional effects." AIMS Materials Science 9, no. 3 (2022): 382–405. http://dx.doi.org/10.3934/matersci.2022023.

Full text

Abstract:

<abstract><p>Quantum correlations phenomena, such as entanglement, quantum discord and quantum coherence, are ubiquitous effects caused by interactions between physical systems—such as electrons and ions in a piece of metal, or H atoms/molecules adsorbed in nanoporous materials. Here, we address time-asymmetric quantumness of correlations (QoC), with particular emphasis on their energetic consequences for dynamics and non-equilibrium thermodynamics in condensed matter and/or many-body systems. Some known theoretical models—for example, the quantum Zeno effect and GKSL-type Markovian equations-of-motion, all of them being time-asymmetric—are shortly considered, with emphasis on the general character of one of their common and most intriguing result. Namely, that in clear contradistinction to conventional expectations, degradation (or destruction, decoherence, consumption, smearing out, coarse-graining) of quantum correlations can be a source of work (instead of heat production). The experimental relevance of the theoretical considerations is shown with the aid of a recent scattering experiment exploring the impulsively driven (by neutron collisions) translational dynamics of H$ _2 $ molecules in carbon nanotubes and other nanostructured materials—a topic of immediate relevance for material sciences and related technologies.</p></abstract>

APA, Harvard, Vancouver, ISO, and other styles

45

Dorofeyev, Illarion. "Quasi-equilibrium relaxation of two identical quantum oscillators with arbitrary coupling strength." Canadian Journal of Physics 93, no. 7 (July 2015): 750–59. http://dx.doi.org/10.1139/cjp-2014-0376.

Full text

Abstract:

This paper deals with the problem of open systems out of equilibrium. An analytical expression for a time-dependent density matrix of two arbitrarily coupled identical quantum oscillators interacting with separate reservoirs is derived using path integral methods. The temporal behavior of spatial variances and of covariance from given initial values up to stationary values is investigated. It is shown that at comparatively low coupling strengths, the asymptotic variances in the long-time limit achieve steady states independently of initial values. Stationary variances differ from the case of total equilibrium due to their coupling with separate thermal reservoirs of different temperatures. The larger the difference in temperatures of thermal baths, the larger is the difference of the stationary values of variances of coupled oscillators compared with values given by the fluctuation dissipation theorem. At strong couplings the variances have divergent character in the framework of the accepted model. Otherwise, in the weak coupling limit the asymptotic stationary variances are always in accordance with the fluctuation dissipation theorem with some accuracy.

APA, Harvard, Vancouver, ISO, and other styles

46

Hess, P. W., P. Becker, H. B. Kaplan, A. Kyprianidis, A. C. Lee, B. Neyenhuis, G. Pagano, et al. "Non-thermalization in trapped atomic ion spin chains." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2108 (October 30, 2017): 20170107. http://dx.doi.org/10.1098/rsta.2017.0107.

Full text

Abstract:

Linear arrays of trapped and laser-cooled atomic ions are a versatile platform for studying strongly interacting many-body quantum systems. Effective spins are encoded in long-lived electronic levels of each ion and made to interact through laser-mediated optical dipole forces. The advantages of experiments with cold trapped ions, including high spatio-temporal resolution, decoupling from the external environment and control over the system Hamiltonian, are used to measure quantum effects not always accessible in natural condensed matter samples. In this review, we highlight recent work using trapped ions to explore a variety of non-ergodic phenomena in long-range interacting spin models, effects that are heralded by the memory of out-of-equilibrium initial conditions. We observe long-lived memory in static magnetizations for quenched many-body localization and prethermalization, while memory is preserved in the periodic oscillations of a driven discrete time crystal state. This article is part of the themed issue ‘Breakdown of ergodicity in quantum systems: from solids to synthetic matter’.

APA, Harvard, Vancouver, ISO, and other styles

47

Rossi, Lorenzo, Fabrizio Dolcini, Fabio Cavaliere, Niccolò Traverso Ziani, Maura Sassetti, and Fausto Rossi. "Signature of Generalized Gibbs Ensemble Deviation from Equilibrium: Negative Absorption Induced by a Local Quench." Entropy 23, no. 2 (February 11, 2021): 220. http://dx.doi.org/10.3390/e23020220.

Full text

Abstract:

When a parameter quench is performed in an isolated quantum system with a complete set of constants of motion, its out of equilibrium dynamics is considered to be well captured by the Generalized Gibbs Ensemble (GGE), characterized by a set {λα} of coefficients related to the constants of motion. We determine the most elementary GGE deviation from the equilibrium distribution that leads to detectable effects. By quenching a suitable local attractive potential in a one-dimensional electron system, the resulting GGE differs from equilibrium by only one single λα, corresponding to the emergence of an only partially occupied bound state lying below a fully occupied continuum of states. The effect is shown to induce optical gain, i.e., a negative peak in the absorption spectrum, indicating the stimulated emission of radiation, enabling one to identify GGE signatures in fermionic systems through optical measurements. We discuss the implementation in realistic setups.

APA, Harvard, Vancouver, ISO, and other styles

48

Martinez-Azcona, Pablo, and Aurélia Chenu. "Analyticity constraints bound the decay of the spectral form factor." Quantum 6 (November 3, 2022): 852. http://dx.doi.org/10.22331/q-2022-11-03-852.

Full text

Abstract:

Quantum chaos cannot develop faster than λ≤2π/(ℏβ) for systems in thermal equilibrium [Maldacena, Shenker & Stanford, JHEP (2016)]. This `MSS bound' on the Lyapunov exponent λ is set by the width of the strip on which the regularized out-of-time-order correlator is analytic. We show that similar constraints also bound the decay of the spectral form factor (SFF), that measures spectral correlation and is defined from the Fourier transform of the two-level correlation function. Specifically, the inflection exponentη, that we introduce to characterize the early-time decay of the SFF, is bounded as η≤π/(2ℏβ). This bound is universal and exists outside of the chaotic regime. The results are illustrated in systems with regular, chaotic, and tunable dynamics, namely the single-particle harmonic oscillator, the many-particle Calogero-Sutherland model, an ensemble from random matrix theory, and the quantum kicked top. The relation of the derived bound with other known bounds, including quantum speed limits, is discussed.

APA, Harvard, Vancouver, ISO, and other styles

49

Schlüter, Henrik, Florian Gayk, Heinz-Jürgen Schmidt, Andreas Honecker, and Jürgen Schnack. "Accuracy of the typicality approach using Chebyshev polynomials." Zeitschrift für Naturforschung A 76, no. 9 (June 21, 2021): 823–34. http://dx.doi.org/10.1515/zna-2021-0116.

Full text

Abstract:

Abstract Trace estimators allow us to approximate thermodynamic equilibrium observables with astonishing accuracy. A prominent representative is the finite-temperature Lanczos method (FTLM) which relies on a Krylov space expansion of the exponential describing the Boltzmann weights. Here we report investigations of an alternative approach which employs Chebyshev polynomials. This method turns out to be also very accurate in general, but shows systematic inaccuracies at low temperatures that can be traced back to an improper behavior of the approximated density of states with and without smoothing kernel. Applications to archetypical quantum spin systems are discussed as examples.

APA, Harvard, Vancouver, ISO, and other styles

50

HIRAYAMA, YOSHIRO. "NUCLEAR-SPIN-BASED MEASUREMENTS OF QUANTUM HALL SYSTEMS." International Journal of Modern Physics B 23, no. 12n13 (May 20, 2009): 2737–38. http://dx.doi.org/10.1142/s0217979209062281.

Full text

Abstract:

Nuclear magnetic resonance (NMR) is widely used in the physical, chemical, and biological sciences. However, conventional NMR techniques based on induction-detection have drawbacks of low-sensitivity and the need of a relatively large sample. It is not suitable to investigate single or double layers (or their nanostructure), which is essential in studying quantum Hall (QH) effects. In this presentation, I discussed a resistively-detected technique to overcome the low-sensitivity limitation of conventional NMR and its application to QH systems. Resistively-detected nuclear-spin-based measurements rely on enhanced interactions between electron and nuclear spins at the degenerate point of different electron-spin states. For example, at the ν = 2/3 degenerate point in a AlGaAs / GaAs system,1–3 nuclear-spin polarization far beyond the thermal equilibrium is generated using current flow (dynamic nuclear-spin polarization). Moreover, nuclear-spin polarization can be detected as enhanced resistance, which is proportional to the magnetization, Mz, of nuclear spins.2 It should be stressed that the special states of ν = 2/3 are needed for dynamic nuclear-spin polarization and Mz detection, but we can apply NMR spectrum and nuclear-spin relaxation (T1 time) measurements for any state we want to estimate. These nuclear-spin-based measurements were successfully applied to characterize QH systems, especially their electron-spin features, using single and double layer systems where characteristics are controlled electrically by the gate biases. For a single layer, we could clarify skyrmion,2 spin-polarization of composite fermion,4 and enhanced spin-orbit interactions in a strongly asymmetric confinement.5 Exciting phases, like a canted antiferromagnetic phase, were studied in a double layer QH system with a total filling factor of 2 (Refs. 6, 7). The low-frequency mode was sensitively detected by monitoring T1, reflecting correlated electron spin features.7 The clear observations of the characteristics, which are difficult to detect in conventional transport and optical measurements, make nuclear-spin-based measurement combined with resistance-detection a versatile and powerful tool for studying QH physics. Possible extensions of such measurements to semiconductor nanosystems were also discussed. The experiments discussed here were mainly carried out at NTT Basic Research Laboratories in collaboration with K. Muraki, N. Kumada, K. Takashina, K. Hashimoto, S. Watanabe and G. Yusa. Note from Publisher: This article contains the abstract only.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Out-of-equilibrium quantum systems'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles