Statics and Dynamics of Weakly Coupled Antiferromagnetic Spin-1/2 Ladders in a Magnetic Field
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

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This 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.

Spin Dynamics in Two-Dimensional Quantum Materials
Spin Dynamics in Two-Dimensional Quantum Materials

Author: Marc Vila Tusell

Publisher: Springer Nature

Published: 2021-11-10

Total Pages: 169

ISBN-13: 3030861147

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This thesis focuses on the exploration of nontrivial spin dynamics in graphene-based devices and topological materials, using realistic theoretical models and state-of-the-art quantum transport methodologies. The main outcomes of this work are: (i) the analysis of the crossover from diffusive to ballistic spin transport regimes in ultraclean graphene nonlocal devices, and (ii) investigation of spin transport and spin dynamics phenomena (such as the (quantum) spin Hall effect) in novel topological materials, such as monolayer Weyl semimetals WeTe2 and MoTe2. Indeed, the ballistic spin transport results are key for further interpretation of ultraclean spintronic devices, and will enable extracting precise values of spin diffusion lengths in diffusive transport and guide experiments in the (quasi)ballistic regime. Furthermore, the thesis provides an in-depth theoretical interpretation of puzzling huge measured efficiencies of the spin Hall effect in MoTe2, as well as a prediction of a novel canted quantum spin Hall effect in WTe2 with spins pointing in the yz plane.

Natural Dynamics of Spin Chains
Natural Dynamics of Spin Chains

Author: Rebecca Juliane Helena Ronke

Publisher:

Published: 2012

Total Pages:

ISBN-13:

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In this thesis, we discuss the natural dynamics of spin chains with regards to their potential role as information carriers in quantum computers and also standalone uses in a quantum computational context. We discuss a range of spin chain devices, expanding existing results on linear chains and simple branched devices to more complex geometries and circular devices. Over the course of this work, we analyse requirements and feasibility of perfect state transfer using the natural dynamics of spin chains and present an extensive investigation into the effects of a number of perturbations on the dynamics of these devices. This includes both fabrication defects and other sources of perturbations. We also present other potential uses of spin chains, including state storage, and introduce an original protocol for the generation of cluster state ladders using only a single linear spin chain.

Dynamics of Quantum Spin Chains from Integrability
Dynamics of Quantum Spin Chains from Integrability

Author: Rogier Pieter Vlijm

Publisher:

Published: 2016

Total Pages: 207

ISBN-13: 9789402802900

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"The study of several quantum magnetic phenomena in this thesis is driven by the experimental realizability of quantum spin chain models of one-dimensional magnetism. The theoretical models employed to study these physical phenomena are integrable quantum spin chains, in particular the anisotropic Heisenberg spin-1/2 model and the Babujan-Takhtajan spin-1 model, while additional (non-)integrable magnetic potentials or spin-spin interactions are considered as well. The dynamics of spin chains are computationally accessible by numerically summing up large amounts of matrix elements of local spin operators between eigenstates of the quantum integrable spin models in a parallelized fashion. The availability of matrix element expressions from quantum integrability constitutes an important connection between the deep mathematical structure of integrable spin chains and experimentally measurable local observables and correlations on magnetic systems. By the aforementioned integrability based method, the dynamics of quasi-particles of quantum spin chains can be assessed. In particular, the scattering effects of bound magnons, the time evolution of spinons, and time-evolution with additional integrability-breaking spin-spin interactions are computed and visualized. Moreover, for several cases the dynamical structure factor is computed, which is relevant to inelastic neutron scattering experiments. Extensions to correlations away from the ground state are investigated, providing opportunities of studying thermal correlations as well."--Samenvatting auteur.