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Littérature scientifique sur le sujet « Low Dimensional Quantum Spin Systems »

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Publié le 7 septembre 2023

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Articles de revues sur le sujet "Low Dimensional Quantum Spin Systems"

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Dillenschneider, Raoul, Jung Hoon Kim et Jung Hoon Han. « Vector Chiral States in Low-Dimensional Quantum-Spin Systems ». Journal of the Korean Physical Society 53, no 2 (14 août 2008) : 732–36. http://dx.doi.org/10.3938/jkps.53.732.

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Wolf, B., S. Zherlitsyn, U. Löw, B. Lüthi, V. Pashchenko et M. Lang. « Low-dimensional quantum spin systems in pulsed magnetic fields ». Physica B : Condensed Matter 346-347 (avril 2004) : 19–26. http://dx.doi.org/10.1016/j.physb.2004.01.013.

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Lemmens, P., G. Güntherodt et C. Gros. « Magnetic light scattering in low-dimensional quantum spin systems ». Physics Reports 375, no 1 (février 2003) : 1–103. http://dx.doi.org/10.1016/s0370-1573(02)00321-6.

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Lima, Leonardo S. « Entanglement Negativity and Concurrence in Some Low-Dimensional Spin Systems ». Entropy 24, no 11 (10 novembre 2022) : 1629. http://dx.doi.org/10.3390/e24111629.

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The influence of magnon bands on entanglement in the antiferromagnetic XXZ model on a triangular lattice, which models the bilayer structure consisting of an antiferromagnetic insulator and normal metal, is investigated. This effect was studied in ferromagnetic as well as antiferromagnetic triangular lattices. Quantum entanglement measures given by the entanglement negativity have been studied, where a magnon current is induced in the antiferromagnet due to interfacial exchange coupling between localized spins in the antiferromagnet and itinerant electrons in a normal metal. Moreover, quantum correlations in other frustrated models, namely the metal-insulation antiferromagnetic bilayer model and the Heisenberg model with biquadratic and bicubic interactions, are analyzed.
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HORVATIĆ, M., et C. BERTHIER. « HIGH FIELD NMR IN STRONGLY CORRELATED LOW-DIMENSIONAL FERMIONIC SYSTEMS ». International Journal of Modern Physics B 16, no 20n22 (30 août 2002) : 3265–70. http://dx.doi.org/10.1142/s0217979202014127.

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We review some recent NMR results obtained in Grenoble High Magnetic Field Laboratory on magnetic field induced phenomena in strongly correlated low-dimensional fermionic systems: i) magnetic field dependence of the soliton lattice in the IC phase of the spin-Peierls system CuGeO3, ii) NMR study of the complete H-T phase diagram of the organo-metallic spin ladder Cu2(C5H12N2)2Cl4, and iii) the first "standard" NMR measurements (i.e., without optical pumping) on 2D electrons in Quantum wells, providing a detailed description of the fractional quantum Hall effect state at ν = 1/2 with the first determination of the corresponding effective polarization mass of composite fermions. Latest study of the ν = 2/3 state revealed, among other features, an unexpected phase transition.
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Ercolessi, Elisa. « ONE AND QUASI-ONE DIMENSIONAL SPIN SYSTEMS ». Modern Physics Letters A 18, no 33n35 (20 novembre 2003) : 2329–36. http://dx.doi.org/10.1142/s0217732303012544.

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Quantum spin models represent one of the most studied examples of application of low-dimensional field theories to condensed matter systems. In this paper we will review some chapters of this hystory, that dates back to the early '80, when Haldane put forward his by now famous conjecture on antiferromagnetic spin chains, and reaches the present days, with the most advanced applications of integrable models and conformal field theory.
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Saha-Dasgupta, Tanusri. « The Fascinating World of Low-Dimensional Quantum Spin Systems : Ab Initio Modeling ». Molecules 26, no 6 (10 mars 2021) : 1522. http://dx.doi.org/10.3390/molecules26061522.

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In recent times, ab initio density functional theory has emerged as a powerful tool for making the connection between models and materials. Insulating transition metal oxides with a small spin forms a fascinating class of strongly correlated systems that exhibit spin-gap states, spin–charge separation, quantum criticality, superconductivity, etc. The coupling between spin, charge, and orbital degrees of freedom makes the chemical insights equally important to the strong correlation effects. In this review, we establish the usefulness of ab initio tools within the framework of the N-th order muffin orbital (NMTO)-downfolding technique in the identification of a spin model of insulating oxides with small spins. The applicability of the method has been demonstrated by drawing on examples from a large number of cases from the cuprate, vanadate, and nickelate families. The method was found to be efficient in terms of the characterization of underlying spin models that account for the measured magnetic data and provide predictions for future experiments.
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Ohta, H., S. Okubo, S. Kimura, T. Sakurai, S. Takeda, T. Tanaka, H. Kikuchi et H. Nagasawa. « Submillimeter-wave ESR measurements of low-dimensional quantum spin systems ». Applied Magnetic Resonance 18, no 4 (avril 2000) : 469–74. http://dx.doi.org/10.1007/bf03162293.

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Wang, Dong-Sheng. « Classes of topological qubits from low-dimensional quantum spin systems ». Annals of Physics 412 (janvier 2020) : 168015. http://dx.doi.org/10.1016/j.aop.2019.168015.

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WOLF, B., S. ZHERLITSYN, S. SCHMIDT, B. LÜTHI et M. LANG. « PULSE-FIELD EXPERIMENTS ON THE SPIN-LATTICE INTERACTION IN LOW-DIMENSIONAL SPIN SYSTEMS ». International Journal of Modern Physics B 16, no 20n22 (30 août 2002) : 3369–72. http://dx.doi.org/10.1142/s0217979202014449.

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Low-dimensional spin systems reveal new and unexpected physical phenomena such as distinct plateaus in the magnetization as a function of magnetic field. In this paper we present ultrasonic measurements for the quasi-two-dimensional spin system SrCu2(BO3)2 in magnetic fields up to 50 T. From this technique we obtained detailed information about the spin state, the magnetic excitations and their interaction with phonons. The dimerized quantum-spin system SrCu2(BO3)2 exhibits plateaus in the magnetization and shows surprisingly strong magneto-elastic effects as a function of temperature and magnetic field. The pronounced elastic anomalies indicate a resonant interaction between the sound wave and the magnetic excitations.
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Thèses sur le sujet "Low Dimensional Quantum Spin Systems"

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Heidrich-Meisner, Fabian. « Transport properties of low-dimensional quantum spin systems ». [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974939242.

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Sugimoto, Takanori. « Dynamical Properties in Low-Dimensional Quantum Spin Systems ». 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157746.

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Hofmann, Michael. « Anomalous heat transport in low dimensional quantum spin systems ». [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964915626.

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Law, Joseph M. « Identification and investigation of new low-dimensional quantum spin systems ». Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8963.

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This thesis focuses on one area of modern condensed matter physics, namely low-dimensional magnetism, and more specifically one-dimensional linear chains. The work herein can be split into three parts. The first part provides a tool for the greater community. I herein propose a Pad´e approximation for the temperature dependent magnetic susceptibility of a S = 3/2 spin chain, that is more accurate than those already known. The approximation allows one to fit experimentally measured magnetic susceptibilities and ascertain values such as the near-neighbour spin exchange interaction and the g-factor. The second and third parts of this thesis are both concerned with experimentally and theoretically characterizing two isostructural linear S = 1/2 chain compounds on opposite ends of the 3d transition metal series. The compounds, CuCrO4 (3d9) and TiPO4 (3d1), are shown to have completely different ground states despite both being largely isostructural and S = 1/2 quantum spin systems. In this work and the resulting publications it is shown that CuCrO4 is a one-dimensional S = 1/2 spin chain with anti-ferromagnetic nearest- and next nearest-neighbour spin exchange interactions. The ratio of these spin exchange interactions is shown experimentally and theoretically to be approximately 2, putting CuCrO4 in the vicinity of the Majumdar-Ghosh point, for which the magnetic ground-state can ii be solved analytically. Small ferromagnetic inter-chain coupling leads to long-range ferromagnetic ordering between anti-ferromagnetic chains at 8.2(2) K. At this temperature a spontaneous electrical polarization is observed. This classifies CuCrO4 as a type-II multiferroic. Contrary to CuCrO4, TiPO4 has a non-magnetic ground state. At 111 and 74 K TiPO4 undergoes a two stage phase transition, which is interpreted as a spin-Peierls transition. There is evidence that below 74 K TiPO4 has a new crystal structure, in which there are alternating dimerised chains and two different PO4 tetrahedral units. Currently the new structure has not been identified and no super-structure reflections have been confirmed in either low-temperature neutron or x-ray diffraction. In summary this thesis presents some experimental and theoretical contributions to the field of low-dimensional magnetism.
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Mendoza, Arenas Juan José. « Spin and energy transport in boundary-driven low-dimensional open quantum systems ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:44b89c4d-e9eb-4136-a540-c80bcabeb6f6.

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In spite of being the subject of intense research, several key but complex questions on the nonequilibrium physics of correlated quantum systems remain controversial. For example, the nature of particle and energy transport in different interacting regimes, the relevance of integrability and the impact of environmental coupling are still under active debate. These problems can now be approached numerically, due to the development of powerful algorithms which allow the efficient simulation of the dynamics of correlated systems. In the present thesis we study numerically and analytically the transport properties of low-dimensional quantum systems. In particular, we consider the steady-state spin and energy conduction through XXZ boundary-driven spin-1/2 chains. In the first part, we analyse the transport through chains with only coherent processes in the bulk. For spin transport induced by a magnetisation imbalance between the boundaries, previously identified ballistic, diffusive and negative differential conductivity regimes are reproduced. We provide a comprehensive explanation of the latter. The energy conduction induced by this driving scheme features the same properties as spin transport. For thermally-driven chains, we discuss the nature of energy transport and the emergence of local thermal states when the integrability of the Hamiltonian is broken. In the second part of the thesis we analyse the effect of bulk incoherent effects on the transport properties previously discussed. First we find that for weak particle-particle interactions, pure dephasing degrades spin and energy conduction. In contrast, for strong interactions dephasing induces a significant transport enhancement. We identify the underlying mechanism and discuss its generality. Finally, motivated by the lattice structure of several organic conductors, we study the interplay between coherent and incoherent processes in systems of weakly-coupled chains. We find an enhancement effect due to incoherent interchain hopping, stronger than that by dephasing, which increases with the chain length and relates to superdiffusive transport.
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Rahnavard, Yousef [Verfasser], et Wolfram [Akademischer Betreuer] Brenig. « Transport and dynamics of low-dimensional quantum spin systems / Yousef Rahnavard ; Betreuer : Wolfram Brenig ». Braunschweig : Technische Universität Braunschweig, 2014. http://d-nb.info/117582089X/34.

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Janson, Oleg. « DFT-based microscopic magnetic modeling for low-dimensional spin systems ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-91976.

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In the vast realm of inorganic materials, the Cu2+-containing cuprates form one of the richest classes. Due to the combined effect of crystal-field, covalency and strong correlations, all undoped cuprates are magnetic insulators with well-localized spins S=1/2, whereas the charge and orbital degrees of freedom are frozen out. The combination of the spin-only nature of their magnetism with the unique structural diversity renders cuprates as excellent model systems. The experimental studies, boosted by the discovery of high-temperature superconductivity in doped La2CuO4, revealed a fascinating variety of magnetic behaviors observed in cuprates. A digest of prominent examples should include the spin-Peierls transition in CuGeO3, the Bose-Einstein condensation of magnons in BaCuSi2O6, and the quantum critical behavior of Li2ZrCuO4. The magnetism of cuprates originates from short-range (typically, well below 1 nm) exchange interactions between pairs of spins Si and Sj, localized on Cu atoms i and j. Especially in low-dimensional compounds, these interactions are strongly anisotropic: even for similar interatomic distances |Rij|, the respective magnetic couplings Jij can vary by several orders of magnitude. On the other hand, there is an empirical evidence for the isotropic nature of this interaction in the spin space: different components of Si are coupled equally strong. Thus, the magnetism of cuprates is mostly described by a Heisenberg model, comprised of Jij(Si*Sj) terms. Although the applicability of this approach to cuprates is settled, the model parameters Jij are specific to a certain material, or more precisely, to a particular arrangement of the constituent atoms, i.e. the crystal structure. Typically, among the infinite number of Jij terms, only several are physically relevant. These leading exchange couplings constitute the (minimal) microscopic magnetic model. Already at the early stages of real material studies, it became gradually evident that the assignment of model parameters is a highly nontrivial task. In general, the problem can be solved experimentally, using elaborate measurements, such as inelastic neutron scattering on large single crystals, yielding the magnetic excitation spectrum. The measured dispersion is fitted using theoretical models, and in this way, the model parameters are refined. Despite excellent accuracy of this method, the measurements require high-quality samples and can be carried out only at special large-scale facilities. Therefore, less demanding (especially, regarding the sample requirements), yet reliable and accurate procedures are desirable. An alternative way to conjecture a magnetic model is the empirical approach, which typically relies on the Goodenough-Kanamori rules. This approach links the magnetic exchange couplings to the relevant structural parameters, such as bond angles. Despite the unbeatable performance of this approach, it is not universally applicable. Moreover, in certain cases the resulting tentative models are erroneous. The recent developments of computational facilities and techniques, especially for strongly correlated systems, turned density-functional theory (DFT) band structure calculations into an appealing alternative, complementary to the experiment. At present, the state-of-the-art computational methods yield accurate numerical estimates for the leading microscopic exchange couplings Jij (error bars typically do not exceed 10-15%). Although this computational approach is often regarded as ab initio, the actual procedure is not parameter-free. Moreover, the numerical results are dependent on the parameterization of the exchange and correlation potential, the type of the double-counting correction, the Hubbard repulsion U etc., thus an accurate choice of these crucial parameters is a prerequisite. In this work, the optimal parameters for cuprates are carefully evaluated based on extensive band structure calculations and subsequent model simulations. Considering the diversity of crystal structures, and consequently, magnetic behaviors, the evaluation of a microscopic model should be carried out in a systematic way. To this end, a multi-step computational approach is developed. The starting point of this procedure is a consideration of the experimental structural data, used as an input for DFT calculations. Next, a minimal DFT-based microscopic magnetic model is evaluated. This part of the study comprises band structure calculations, the analysis of the relevant bands, supercell calculations, and finally, the evaluation of a microscopic magnetic model. The ground state and the magnetic excitation spectrum of the evaluated model are analyzed using various simulation techniques, such as quantum Monte Carlo, exact diagonalization and density-matrix renormalization groups, while the choice of a particular technique is governed by the dimensionality of the model, and the presence or absence of magnetic frustration. To illustrate the performance of the approach and tune the free parameters, the computational scheme is applied to cuprates featuring rather simple, yet diverse magnetic behaviors: spin chains in CuSe2O5, [NO]Cu(NO3)3, and CaCu2(SeO3)2Cl2; quasi-two-dimensional lattices with dimer-like couplings in alpha-Cu2P2O7 and CdCu2(BO3)2, as well as the 3D magnetic model with pronounced 1D correlations in Cu6Si6O18*6H2O. Finally, the approach is applied to spin liquid candidates --- intricate materials featuring kagome-lattice arrangement of the constituent spins. Based on the DFT calculations, microscopic magnetic models are evaluated for herbertsmithite Cu3(Zn0.85Cu0.15)(OH)6Cl2, kapellasite Cu3Zn(OH)6Cl2 and haydeeite Cu3Mg(OH)6Cl2, as well as for volborthite Cu3[V2O7](OH)2*2H2O. The results of the DFT calculations and model simulations are compared to and challenged with the available experimental data. The advantages of the developed approach should be briefly discussed. First, it allows to distinguish between different microscopic models that yield similar macroscopic behavior. One of the most remarkable example is volborthite Cu3[V2O7](OH)2*2H2O, initially described as an anisotropic kagome lattice. The DFT calculations reveal that this compound features strongly coupled frustrated spin chains, thus a completely different type of magnetic frustration is realized. Second, the developed approach is capable of providing accurate estimates for the leading magnetic couplings, and consequently, reliably parameterize the microscopic Hamiltonian. Dioptase Cu6Si6O18*6H2O is an instructive example showing that the microscopic theoretical approach eliminates possible ambiguity and reliably yields the correct parameterization. Third, DFT calculations yield even better accuracy for the ratios of magnetic exchange couplings. This holds also for small interchain or interplane couplings that can be substantially smaller than the leading exchange. Hence, band structure calculations provide a unique possibility to address the interchain or interplane coupling regime, essential for the magnetic ground state, but hardly perceptible in the experiment due to the different energy scales. Finally, an important advantage specific to magnetically frustrated systems should be mentioned. Numerous theoretical and numerical studies evidence that low-dimensionality and frustration effects are typically entwined, and their disentanglement in the experiment is at best challenging. In contrast, the computational procedure allows to distinguish between these two effects, as demonstrated by studying the long-range magnetic ordering transition in quasi-1D spin chain systems. The computational approach presented in the thesis is a powerful tool that can be directly applied to numerous S=1/2 Heisenberg materials. Moreover, with minor modifications, it can be largely extended to other metallates with higher value of spin. Besides the excellent performance of the computational approach, its relevance should be underscored: for all the systems investigated in this work, the DFT-based studies not only reproduced the experimental data, but instead delivered new valuable information on the magnetic properties for each particular compound. Beyond any doubt, further computational studies will yield new surprising results for known as well as for new, yet unexplored compounds. Such "surprising" outcomes can involve the ferromagnetic nature of the couplings that were previously considered antiferromagnetic, unexpected long-range couplings, or the subtle balance of antiferromagnetic and ferromagnetic contributions that "switches off" the respective magnetic exchange. In this way, dozens of potentially interesting systems can acquire quantitative microscopic magnetic models. The results of this work evidence that elaborate experimental methods and the DFT-based modeling are of comparable reliability and complement each other. In this way, the advantageous combination of theory and experiment can largely advance the research in the field of low-dimensional quantum magnetism. For practical applications, the excellent predictive power of the computational approach can largely alleviate designing materials with specific properties.
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Lipps, Ferdinand. « Electron spins in reduced dimensions : ESR spectroscopy on semiconductor heterostructures and spin chain compounds ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-74470.

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Spatial confinement of electrons and their interactions as well as confinement of the spin dimensionality often yield drastic changes of the electronic and magnetic properties of solids. Novel quantum transport and optical phenomena, involving electronic spin degrees of freedom in semiconductor heterostructures, as well as a rich variety of exotic quantum ground states and magnetic excitations in complex transition metal oxides that arise upon such confinements, belong therefore to topical problems of contemporary condensed matter physics. In this work electron spin systems in reduced dimensions are studied with Electron Spin Resonance (ESR) spectroscopy, a method which can provide important information on the energy spectrum of the spin states, spin dynamics, and magnetic correlations. The studied systems include quasi onedimensional spin chain materials based on transition metals Cu and Ni. Another class of materials are semiconductor heterostructures made of Si and Ge. Part I deals with the theoretical background of ESR and the description of the experimental ESR setups used which have been optimized for the purposes of the present work. In particular, the development and implementation of axial and transverse cylindrical resonant cavities for high-field highfrequency ESR experiments is discussed. The high quality factors of these cavities allow for sensitive measurements on μm-sized samples. They are used for the investigations on the spin-chain materials. The implementation and characterization of a setup for electrical detected magnetic resonance is presented. In Part II ESR studies and complementary results of other experimental techniques on two spin chain materials are presented. The Cu-based material Linarite is investigated in the paramagnetic regime above T > 2.8 K. This natural crystal constitutes a highly frustrated spin 1/2 Heisenberg chain with ferromagnetic nearest-neighbor and antiferromagnetic next-nearestneighbor interactions. The ESR data reveals that the significant magnetic anisotropy is due to anisotropy of the g-factor. Quantitative analysis of the critical broadening of the linewidth suggest appreciable interchain and interlayer spin correlations well above the ordering temperature. The Ni-based system is an organic-anorganic hybrid material where the Ni2+ ions possessing the integer spin S = 1 are magnetically coupled along one spatial direction. Indeed, the ESR study reveals an isotropic spin-1 Heisenberg chain in this system which unlike the Cu half integer spin-1/2 chain is expected to possess a qualitatively different non-magnetic singlet ground state separated from an excited magnetic state by a so-called Haldane gap. Surprisingly, in contrast to the expected Haldane behavior a competition between a magnetically ordered ground state and a potentially gapped state is revealed. In Part III investigations on SiGe/Si quantum dot structures are presented. The ESR investigations reveal narrowlines close to the free electron g-factor associated with electrons on the quantum dots. Their dephasing and relaxation times are determined. Manipulations with sub-bandgap light allow to change the relative population between the observed states. On the basis of extensive characterizations, strain, electronic structure and confined states on the Si-based structures are modeled with the program nextnano3. A qualitative model, explaining the energy spectrum of the spin states is proposed.
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Carvalho, Julio Garcia. « Propriedades dinâmicas em sistemas quânticos de muitos corpos ». [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277848.

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Orientador: Guillermo Gerardo Cabrera Oyarzun
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
Abstract: Quantum spin systems are caracterized by huge spaces of states, whose dimensions grow exponentially with the particles number. If following the preparation of the initial state, the system is kept isolated from external variables, it will develop a unitary time evolution according to Schrödinger equation or to Liouville equation. The system is driven exclusively by quantum uctuations, whose origin is the Uncertainty Principle. The evolution of a quantum state or a physical observable or mathematical nonobservable operator mean values may involve all states of the whole space of states, or big or small fractions of the total number of states. The analysis of the relaxation of a spin system from an arbitrary initial state to the equilibrium has to cope in general with the difficulty of requiring an extraordinarily great number of eigenstates and eigenvalues. In this work the main interest is centered on the evolution of magnetization¿s Fourier components in low dimensional systems of spins 1/2, whose interactions be given by the exchange modeled by Heisenberg Hamiltonians with axial anisotopy, XXZ. Exact solutions, analitic or numeric, are obtained. This is the continuation of work done in our research group which dealt with XY Hamiltonian families. In the analysis of the systems with the Hamiltonian XXZ, it was specially analysed the subspace defined by null total magnetization and the subspace defined by one spin wave, where chains up to 14 and 1200 were treated, respectively. There are emergence of fast and slow relaxation processes, which depend on the interations and on the initial state, and which result from destructive or constructive quantum interferences. Connections between the presence of those processes and the energy spectrum structure is discussed. Finally, the time evolution of some measures of global entanglement from initial states in the subspace of one spin wave are analised: the considered dynamics creates global entanglement until each entanglement measure reaches a saturation
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Resumo: Os sistemas quânticos de spin são caracterizados por espaços de estados muito grandes, cujas dimensões crescem exponencialmente com o número de partículas. Se após a preparação do estado inicial, o sistema for mantido isolado de variáveis externas, desenvolve-se uma evolução temporal unitária prescrita pela equação de Schrödinger ou pela equação de Liouville. O sistema é movido exclusivamente por flutuações quânticas, as quais têm sua origem no Princípio da Incerteza. A evolução de um estado quântico ou de valores médios de observáveis físicos ou de operadores matemáticos não observáveis pode envolver todos os estados do espaço de estados, ou frações grandes ou pequenas do número total de estados. A análise da relaxação de um sistema de spins desde um estado inicial arbitrário até o equilíbrio apresenta a dificuldade de requerer em geral um número extraordinariamente grande de auto-estados e autovalores. Neste trabalho o maior interesse está na evolução das componentes de Fourier da magnetização em sistemas de baixa dimensão espacial, com spins 1/2 e cujas interações sejam dadas pela troca modelada por Hamiltonianos de Heisenberg com anisotropia axial, XXZ. Serão obtidas soluções exatas: numéricas ou analíticas. A motivação proveio de trabalhos anteriores realizados no grupo de pesquisa referentes a famílias do Hamiltoniano XY. Ao se considerar o Hamiltoniano XXZ, analisou-se especialmente o subespaço definido por magnetização total nula e o subespa¸ co de uma onda de spin, onde trataram-se cadeias com até 14 e 1200 sítios, respectivamente. Há emergência de processos rápidos e lentos de relaxação, os quais dependem das interações e do estado inicial, e resultam de interferência quântica destrutiva ou construtiva. Serão discutidas conexões entre a presença desses processos e a estrutura do espectro de energia. Finalmente serão analisadas as evoluções temporais de algumas medidas de emaranhamento global, a partir de estados contidos no subespaço de uma onda de spin: a dinâmica considerada cria emaranhamento global até cada medida atingir uma saturação
Doutorado
Física da Matéria Condensada
Doutor em Ciências
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Grijalva, Sebastian. « Boundary effects in quantum spin chains and Finite Size Effects in the Toroidal Correlated Percolation model ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP093.

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Cette thèse est divisée en deux parties : la première présente un modèle statistique en deux dimensions de percolation corrélée sur un réseau toroïdal. Nous présentons un protocole pour construire des surfaces corrélées à longue portée sur la base de surfaces gaussiennes fractionnaires, puis nous relions les ensembles de niveaux à une famille de modèles de percolation corrélés. Les clusters émergents sont ensuite étudiés numériquement, et nous testons leur symétrie conforme en vérifiant que les corrections de taille finie de connectivité à deux points suivent les prédictions de la théorie des champs conformes. Nous commentons également le comportement des fonctions à trois points et fournissons un code numérique pour reproduire les résultats. La deuxième partie de la thèse étudie la chaîne quantique XXZ intégrable de spin-1/2 avec des conditions aux bords ouvertes, pour un nombre pair et impair de sites. Dans régime antiferromagnétique, nous utilisons l'Ansatz de Bethe Algébrique pour déterminer les configurations possibles en termes des champs aux bords. On retrouve les conditions d'existence d'états fondamentaux quasi dégénérés séparés par un gap au reste du spectre. Nous calculons l'aimantation au bord à température nulle et constatons qu'elle dépend du champ sur le bord opposé même dans la limite de chaîne semi-infinie. Nous calculons enfin la fonction d'autocorrélation temporelle au bord et montrons que dans le cas de taille paire, elle est finie à la limite de temps long à cause de la quasi-dégénérescence
This thesis is divided in two parts: The first one presents a 2D statistical model of correlated percolation on a toroidal lattice. We present a protocol to construct long-range correlated surfaces based on fractional Gaussian surfaces and then we relate the level sets to a family of correlated percolation models. The emerging clusters are then numerically studied, and we test their conformal symmetry by verifying that their planar-limit finite-size corrections follow the predictions of Conformal Field Theory. We comment also the behavior of three-point functions and provide a numerical code to reproduce the results.The second part of the thesis studies the quantum integrable XXZ spin-1/2 chain with open boundary conditions for even and odd number of sites. We concentrate in the anti-ferromagnetic regime and use the Algebraic Bethe Ansatz to determine the configurations that arise in terms of the boundary fields. We find the conditions of existence of quasi-degenerate ground states separated by a gap to the rest of the spectrum. We calculate the boundary magnetization at zero temperature and find that it depends on the field at the opposite edge even in the semi-infinite chain limit. We finally calculate the time autocorrelation function at the boundary and show that in the even-size case it is finite for the long-time limit as a result of the quasi-degeneracy
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Livres sur le sujet "Low Dimensional Quantum Spin Systems"

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Hayward, Carol Ann. Quantum mechanics in low-dimensional spin systems. Birmingham : University of Birmingham, 1994.

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Vanderstraeten, Laurens. Tensor Network States and Effective Particles for Low-Dimensional Quantum Spin Systems. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-64191-1.

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Quantum theory of one-dimensional spin systems. Cambridge, UK : Cambridge Scientific Publishers, 2010.

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Seki, Shinichiro. Magnetoelectric Response in Low-Dimensional Frustrated Spin Systems. Tokyo : Springer Japan, 2012. http://dx.doi.org/10.1007/978-4-431-54091-5.

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service), SpringerLink (Online, dir. Magnetoelectric Response in Low-Dimensional Frustrated Spin Systems. Tokyo : Springer Japan, 2012.

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Bauer, Günther. Low-Dimensional Electronic Systems : New Concepts. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992.

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NATO Advanced Research Workshop on Optical Switching in Low-Dimensional Systems (1988 Marbella, Spain). Optical switching in low-dimensional systems. New York : Plenum Press, 1989.

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Morandi, Giuseppe. Field Theories for Low-Dimensional Condensed Matter Systems : Spin Systems and Strongly Correlated Electrons. Berlin, Heidelberg : Springer Berlin Heidelberg, 2000.

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Giuseppe, Morandi, dir. Field theories for low-dimensional condensed matter systems : Spin systems and strongly correlated electrons. Berlin : Springer, 2000.

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1927-, Balkanski Minko, et Andreev Nikolai, dir. Advanced electronic technologies and systems based on low-dimensional quantum devices. Dordrecht : Kluwer Academic Publishers, 1997.

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Chapitres de livres sur le sujet "Low Dimensional Quantum Spin Systems"

1

Bose, Indrani. « Low-dimensional Quantum Spin Systems ». Dans Field Theories in Condensed Matter Physics, 359–408. Gurgaon : Hindustan Book Agency, 2001. http://dx.doi.org/10.1007/978-93-86279-07-1_8.

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Grüninger, Markus, Marco Windt, Eva Benckiser, Tamara S. Nunner, Kai P. Schmidt, Götz S. Uhrig et Thilo Kopp. « Optical Spectroscopy of Low-Dimensional Quantum Spin Systems ». Dans Advances in Solid State Physics, 95–112. Berlin, Heidelberg : Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-44838-9_7.

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Laflorencie, Nicolas, et Didier Poilblanc. « Simulations of pure and doped low-dimensional spin-1/2 gapped systems ». Dans Quantum Magnetism, 227–52. Berlin, Heidelberg : Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/bfb0119595.

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Sorella, S., et Q. F. Zhong. « Spin-Charge Decoupling and the One-Hole Green’s Function in a Quantum Antiferromagnet ». Dans Correlation Effects in Low-Dimensional Electron Systems, 185–89. Berlin, Heidelberg : Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-85129-2_20.

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Haldane, F. D. M. « Physics of the Ideal Semion Gas : Spinons and Quantum Symmetries of the Integrable Haldane-Shastry Spin Chain ». Dans Correlation Effects in Low-Dimensional Electron Systems, 3–20. Berlin, Heidelberg : Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-85129-2_1.

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Eto, M., et Yu V. Nazarov. « Enhancement of Kondo Effect Due to Spin-Singlet-Triplet Competition in Quantum Dots ». Dans Kondo Effect and Dephasing in Low-Dimensional Metallic Systems, 203–6. Dordrecht : Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0427-5_24.

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Mennerich, C., H. H. Klauss, A. U. B. Wolter, S. Süllow, F. J. Litterst, C. Golze, R. Klingeler et al. « High Field Level Crossing Studies on Spin Dimers in the Low Dimensional Quantum Spin System Na2T2(C2O2)3(H2O)2 with T = Ni, Co, Fe, Mn ». Dans NATO Science for Peace and Security Series B : Physics and Biophysics, 97–124. Dordrecht : Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-8512-3_8.

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Weber, W., S. Riesen et D. Oberli. « Spin-Dependent Transmission and Spin Precession of Electrons Passing Across Ferromagnets ». Dans Physics of Low Dimensional Systems, 351–61. Boston, MA : Springer US, 2001. http://dx.doi.org/10.1007/0-306-47111-6_33.

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Siegmann, H. C. « Spin-Polarized Electrons and Magnetism 2000 ». Dans Physics of Low Dimensional Systems, 1–14. Boston, MA : Springer US, 2001. http://dx.doi.org/10.1007/0-306-47111-6_1.

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Farago, P. S., et K. Blum. « Magnetised Foil as a Spin Filter ». Dans Physics of Low Dimensional Systems, 401–9. Boston, MA : Springer US, 2001. http://dx.doi.org/10.1007/0-306-47111-6_38.

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Actes de conférences sur le sujet "Low Dimensional Quantum Spin Systems"

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Hase, Masashi, Masanori Kohno, Hideaki Kitazawa, Osamu Suzuki, Kiyoshi Ozawa, Giyuu Kido, Motoharu Imai et Xiao Hu. « Magnetic Properties Of The Low-Dimensional Quantum Spin System Cu2CdB2O6 ». Dans LOW TEMPERATURE PHYSICS : 24th International Conference on Low Temperature Physics - LT24. AIP, 2006. http://dx.doi.org/10.1063/1.2355059.

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Sandvik, A. W. « Valence-bond-solid phases and quantum phase transitions in two-dimensional spin models with four-site interactions ». Dans EFFECTIVE MODELS FOR LOW-DIMENSIONAL STRONGLY CORRELATED SYSTEMS. AIP, 2006. http://dx.doi.org/10.1063/1.2178047.

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Tojo, Tatsuki, et Kyozaburo Takeda. « Hole Spin Current Induced by Rashba Spin–Orbit Interaction in Diamond Two-Dimensional Quantum Well System ». Dans Proceedings of the 29th International Conference on Low Temperature Physics (LT29). Journal of the Physical Society of Japan, 2023. http://dx.doi.org/10.7566/jpscp.38.011017.

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Wada, Osamu, Yasuo Yoshida, Yuji Inagaki, Takayuki Asano, Tatsuya Kawae, Kenji Takeo, Takuo Sakon, Kazuyoshi Takeda, Mitsuhiro Motokawa et Yoshitami Ajiro. « Field-Induced Magnetic Ordering in an S = 1/2 Quasi-One-Dimensional Quantum Spin System : (CH3)2NH2Cucl3 ». Dans LOW TEMPERATURE PHYSICS : 24th International Conference on Low Temperature Physics - LT24. AIP, 2006. http://dx.doi.org/10.1063/1.2355048.

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Baumberg, J. J., S. A. Crooker, F. Flack, N. Samarth et D. D. Awschalom. « Ultrafast Coherent Spin Torques in Magnetic Quantum Wells ». Dans International Conference on Ultrafast Phenomena. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.pdp.1.

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Résumé :
Introducing magnetic material into semiconductor nanostructures evokes potent magnetic tuning of the spin-split energy levels due to the strong exchange coupling between the quantum-confined charge carriers and the sublattice of magnetic ions. By uniting low-dimensional magnetic heterostructures with ultrafast spin spectroscopy we discover a new aspect to these systems, the exchange-coupled spin torques acting on both photoinjected carriers and the embedded local moments. Our time-resolved Faraday rotation technique1 identifies the initial injection of spin-polarized carriers, multi-terahertz precession of the electrons, and the coherent transfer of hole angular momentum to the magnetic subsystem via the ultrafast rotation of the local moments. The perturbed ions then undergo free-induction decay, thus enabling the first time-domain all-optical electron spin resonance (ESR) measurements in submonolayer magnetic planes.
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Hitachi, K., M. Yamamoto et S. Tarucha. « Probing Spin States in Quantum Dots by Spin-resolved One-dimensional Contacts ». Dans LOW TEMPERATURE PHYSICS : 24th International Conference on Low Temperature Physics - LT24. AIP, 2006. http://dx.doi.org/10.1063/1.2355215.

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Oestreich, M., S. Hallstein, R. Nötzel, K. Ploog, E. Bauser, W. W. Rühle et K. Köhler. « Spin quantum beats in bulk and low dimensional semiconductors ». Dans International Conference on Ultrafast Phenomena. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.wc.5.

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The electron Landé g factor is one of the basic parameters in semiconductors which de scribes the magnitude of the Zeeman splitting of electronic states in magnetic fields. Since various theoretical models predict the value of g, accurate measurements of g provide a sensitive test of different band structure calculations. A recently introduced experimental technique enables the measurement of the electron g factor g* with high accuracy by spin quantum beats. [1] The technique proves to be feasible to measure various effects as the anisotropy of g* in quantum wires,[2] the dependence of g* on quantum well thickness,[3] and the temperature dependence of g* in bulk GaAs up to room temperature. [4, 5] The temperature dependent spin quantum beat experiments show interesting discrepancies between experiment and a well accepted five-band k→⋅p→ theory model.[4]
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Pellegrini, Vittorio, S. Luin, A. Pinczuk, B. S. Dennis, L. N. Pfeiffer et K. W. West. « Inelastic light scattering spectroscopy of collective spin excitations in low-dimensional semiconductors : Evidence for excitonic instabilities ». Dans International Quantum Electronics Conference. Washington, D.C. : OSA, 2004. http://dx.doi.org/10.1364/iqec.2004.ithk2.

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WOLF, B., S. ZHERLITSYN, S. SCHMIDT, B. LÜTHI et M. LANG. « PULSE-FIELD EXPERIMENTS ON THE SPIN-LATTICE INTERACTION IN LOW-DIMENSIONAL SPIN SYSTEMS ». Dans Physical Phenomena at High Magnetic Fields - IV. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812777805_0125.

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Kenji Kashima et Kazunori Nishio. « Global stabilization of two-dimensional quantum spin systems despite estimation delay ». Dans 2007 46th IEEE Conference on Decision and Control. IEEE, 2007. http://dx.doi.org/10.1109/cdc.2007.4434611.

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Rapports d'organisations sur le sujet "Low Dimensional Quantum Spin Systems"

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Mani, R. G., V. Narayanamurti, V. Privman et Y. Zhang. Measurement and Manipulation of Nuclear Spins Embedded in Low Dimensional Quantum Hall Electronic Semiconductor Systems : A Novel Experimental Approach to Quantum Computation. Fort Belvoir, VA : Defense Technical Information Center, mai 2005. http://dx.doi.org/10.21236/ada433744.

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Ullrich, Carsten A. Collective charge and spin dynamics in low-dimensional itinerant electron systems with spin-orbit coupling. Office of Scientific and Technical Information (OSTI), septembre 2019. http://dx.doi.org/10.2172/1566830.

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