Dynamical Correlations of Low Dimensional Quantum Magnets
Author: Andrew A. J. James
Publisher:
Published: 2008
Total Pages: 226
ISBN-13:
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Statics and Dynamics of Weakly Coupled Antiferromagnetic Spin-1/2 Ladders in a Magnetic Field
Author: Pierre Bouillot
Publisher: Springer Science & Business Media
Published: 2012-12-14
Total Pages: 104
ISBN-13: 3642338089
DOWNLOAD EBOOKThis thesis shows how a combination of analytic and numerical techniques, such as a time dependent and finite temperature Density Matrix Renormalization Group (DMRG) technique, can be used to obtain the physical properties of low dimensional quantum magnets with an unprecedented level of accuracy. A comparison between the theory and experiment then enables these systems to be used as quantum simulators; for example, to test various generic properties of low dimensional systems such as Luttinger liquid physics, the paradigm of one dimensional interacting quantum systems. Application of these techniques to a material made of weakly coupled ladders (BPCB) allowed the first quantitative test of Luttinger liquids. In addition, other physical quantities (magnetization, specific heat etc.), and more remarkably the spins-spin correlations – directly measurable in neutron scattering experiments – were in excellent agreement with the observed quantities. We thus now have tools to quantitatiively assess the dynamics for this class of quantum systems.
Finite-temperature Dynamics of Low-dimensional Quantum Systems with DMRG Methods
Author: Alexander Clemens Tiegel
Publisher:
Published: 2016
Total Pages: 0
ISBN-13:
DOWNLOAD EBOOKThis thesis is concerned with the numerical study of one-dimensional (1D) spin-1/2 quantum magnets and related method development. Its focus is on the calculation of dynamical spin correlation functions both at zero and finite temperature. This is motivated by the accessibility of dynamical quantities in experiments such as inelastic neutron scattering (INS) and electron spin resonance (ESR). The numerical methods used in this thesis are based on extensions of the density-matrix renormalization group (DMRG) and are formulated in the framework of matrix product states (MPS). While zero-tempe...
Magnetic Field Effects in Low-Dimensional Quantum Magnets
Author: Adam Iaizzi
Publisher: Springer
Published: 2018-11-28
Total Pages: 156
ISBN-13: 3030018032
DOWNLOAD EBOOKThis thesis is a tour-de-force combination of analytic and computational results clarifying and resolving important questions about the nature of quantum phase transitions in one- and two-dimensional magnetic systems. The author presents a comprehensive study of a low-dimensional spin-half quantum antiferromagnet (the J-Q model) in the presence of a magnetic field in both one and two dimensions, demonstrating the causes of metamagnetism in such systems and providing direct evidence of fractionalized excitations near the deconfined quantum critical point. In addition to describing significant new research results, this thesis also provides the non-expert with a clear understanding of the nature and importance of computational physics and its role in condensed matter physics as well as the nature of phase transitions, both classical and quantum. It also contains an elegant and detailed but accessible summary of the methods used in the thesis—exact diagonalization, Monte Carlo, quantum Monte Carlo and the stochastic series expansion—that will serve as a valuable pedagogical introduction to students beginning in this field.
Dynamic Correlations in One-dimensional Quantum Magnets at Finite Temperature
Author: Benedikt Fauseweh
Publisher:
Published: 2016
Total Pages: 0
ISBN-13:
DOWNLOAD EBOOKCharacterizing Ground States of Low-dimensional Quantum Magnets
Author: Hyejin Ju
Publisher:
Published: 2013
Total Pages: 196
ISBN-13: 9781303052262
DOWNLOAD EBOOKThe study of frustration in quantum magnetism has been the focus of extensive research in the past couple of decades. The class of materials in this category is typically strongly correlated, due to strong electron-electron repulsion. In one- and two-dimensions, quantum fluctuations dominate these systems, and often, semi-classical approximations become an oversimplification. This thesis is concerned with exploring exotic physics that can emerge in low-dimensional quantum magnets. First, we use a T = 0 projected Monte Carlo algorithm in the valence bond basis to study the entanglement scaling of two-dimensional (2d) gapless systems. In particular, we focus on the resonating-valence-bond wavefunction as well as the gapless Goldstone mode in the Heisenberg model on the square lattice. We find that, in addition to the area law, there is a subleading, shape-dependent piece to the entanglement entropy, which is reminiscent of one dimensional (1d) gapless systems. We then explore the Heisenberg model under an applied magnetic field on the quasi-1d problem of a three-leg triangular spin tube (TST), using extensive density-matrix-renormalization group calculations coupled with analytical arguments to describe the results. We find that the physics describing this model differs from some of the well-known results on the two dimensional lattice, especially near low magnetic fields and at 1/3 magnetization. Finally, further research and possibilities in numerical techniques are discussed.
Tensor Network States and Effective Particles for Low-Dimensional Quantum Spin Systems
Author: Laurens Vanderstraeten
Publisher: Springer
Published: 2017-08-10
Total Pages: 229
ISBN-13: 3319641913
DOWNLOAD EBOOKThis thesis develops new techniques for simulating the low-energy behaviour of quantum spin systems in one and two dimensions. Combining these developments, it subsequently uses the formalism of tensor network states to derive an effective particle description for one- and two-dimensional spin systems that exhibit strong quantum correlations. These techniques arise from the combination of two themes in many-particle physics: (i) the concept of quasiparticles as the effective low-energy degrees of freedom in a condensed-matter system, and (ii) entanglement as the characteristic feature for describing quantum phases of matter. Whereas the former gave rise to the use of effective field theories for understanding many-particle systems, the latter led to the development of tensor network states as a description of the entanglement distribution in quantum low-energy states.
New Theoretical Approaches to Strongly Correlated Systems
Author: Alexei M. Tsvelik
Publisher: Springer
Published:
Total Pages: 301
ISBN-13: 9789401008396
DOWNLOAD EBOOKFor many years, the physics of strongly correlated systems was considered a theorists' playground, right at the border with pure mathematics, where physicists from the `real world' did not venture. The time has come, however, when healthy physics cannot exist without these techniques and results. Lectures on selected topics in the theory of strongly correlated systems are here presented by the leading experts in the field. Topics covered include a use of the form factor approach in low-dimensional systems, applications of quantum field theory to disorder, and dynamical mean field theory. The main divisions of the book deal with: I) Quantum Critical Points; (II) Strongly Correlated One-Dimensional Systems; (III) Strong Correlations and Disorder; and (IV) Dynamical Mean Field Theory.
Dynamical Properties of Unconventional Magnetic Systems
Author: A.T. Skjeltorp
Publisher: Springer Science & Business Media
Published: 2012-12-06
Total Pages: 378
ISBN-13: 9401149887
DOWNLOAD EBOOKMagnetism encompasses a wide range of systems and physical phenomena, and its study has posed and exposed both important fundamental problems and many practical applications. Recently, several entirely new phenomena have thus been discovered, generated through cooperative behaviour which could not have been predicted from a knowledge of `one-spin' states. At the same time, advances in sample preparation, experimental technique, apparatus and radiation sources, have led to increasing precision in the investigation and exposure of greater subtleties in magnetic thin films, multilayers and other systems. Examples of unexpected and conceptually new phenomena occur in strongly correlated and fluctuating quantum systems, producing effects such as Haldane and spin-Peierls gaps, solitons, quantum spin glasses and spin liquids. The discovery and elucidation of these `emerging properties' is a central theme in modern condensed matter physics. The present book comprises a series of chapters by world experts, covering both theoretical and experimental aspects. The approach is pedagogical and tutorial, but fully up to date, covering the latest research. The level is appropriate to graduate researchers who may either be just moving into the field or who are already active in condensed matter physics.
Charge Dynamics in Low Dimensional Prototype Correlated Systems : a View with High-energy X-rays
Author: Md-Zahid Hasan
Publisher:
Published: 2001
Total Pages: 282
ISBN-13:
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