Extended Kitaev magnetism in magnetic fields
Autor(a) principal: | |
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Data de Publicação: | 2020 |
Tipo de documento: | Dissertação |
Idioma: | eng |
Título da fonte: | Biblioteca Digital de Teses e Dissertações da USP |
Texto Completo: | https://www.teses.usp.br/teses/disponiveis/76/76131/tde-19112020-110752/ |
Resumo: | Over the past years, the physics of Kitaev\'s spin-1/2 honeycomb model and its extensions have attracted enormous interest, fueled by a pursuit of the fundamental understanding as well as experimental realizations of quantum spin-liquid phases. A notorious achievement in this field has been the discovery that, when applied in specific directions, a magnetic field can induce a gapped topological spin liquid in the Kitaev quantum magnet ∝-RuCl3. In parallel, the search for other magnets with strong spin-orbit coupling has resulted in recent proposals of material candidates to host spin-1 and spin-3/2 analogs of the Kitaev interaction. Remarkably, all of these materials display nontrivial responses to magnetic fields, such as strongly anisotropic magnetization processes and novel field-induced states, due to the lack of spin-rotational symmetry. Given such a rich background, this dissertation aims at expanding the current knowledge of the effects of magnetic fields on extended Kitaev systems with three different contributions. First, we employ a combination of linear and nonlinear spin-wave theory to study the ordered field-induced phases of the nearestneighbor Heisenberg-Kitaev model, which is often regarded as a minimal model to describe Kitaev magnetism for different spin quantum numbers S. By developing a consistent 1/S expansion, we analyze the influence of the leading-order quantum fluctuations on physical observables and phase diagrams of the experimentally relevant cases of S = 1/2, 1 and 3/2. Second, we consider a more realistic spin model to describe the low-temperature elastic response of ∝-RuCl3 in an applied magnetic field and small uniaxial pressure. Our results suggest that anomalous features found in experiments are indicative of an intermediate-field quantum paramagnetic regime. Finally, we return to the Heisenberg-Kitaev model in a magnetic field, but by now applying the numerical technique of exact diagonalization for S = 1/2. Besides finding good agreement with our spin-wave calculations, we report possible evidence for a new quantum tricritical point. |
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Extended Kitaev magnetism in magnetic fieldsMagnetismo de Kitaev estendido em campos magnéticosDiagonalização exataExact diagonalizationFrustrated magnetismHeisenberg-Kitaev modelKitaev materialsMagnetismo frustradoMateriais KitaevModelo de Heisenberg-KitaevSpin-wave TheoryTeoria de ondas de spinOver the past years, the physics of Kitaev\'s spin-1/2 honeycomb model and its extensions have attracted enormous interest, fueled by a pursuit of the fundamental understanding as well as experimental realizations of quantum spin-liquid phases. A notorious achievement in this field has been the discovery that, when applied in specific directions, a magnetic field can induce a gapped topological spin liquid in the Kitaev quantum magnet ∝-RuCl3. In parallel, the search for other magnets with strong spin-orbit coupling has resulted in recent proposals of material candidates to host spin-1 and spin-3/2 analogs of the Kitaev interaction. Remarkably, all of these materials display nontrivial responses to magnetic fields, such as strongly anisotropic magnetization processes and novel field-induced states, due to the lack of spin-rotational symmetry. Given such a rich background, this dissertation aims at expanding the current knowledge of the effects of magnetic fields on extended Kitaev systems with three different contributions. First, we employ a combination of linear and nonlinear spin-wave theory to study the ordered field-induced phases of the nearestneighbor Heisenberg-Kitaev model, which is often regarded as a minimal model to describe Kitaev magnetism for different spin quantum numbers S. By developing a consistent 1/S expansion, we analyze the influence of the leading-order quantum fluctuations on physical observables and phase diagrams of the experimentally relevant cases of S = 1/2, 1 and 3/2. Second, we consider a more realistic spin model to describe the low-temperature elastic response of ∝-RuCl3 in an applied magnetic field and small uniaxial pressure. Our results suggest that anomalous features found in experiments are indicative of an intermediate-field quantum paramagnetic regime. Finally, we return to the Heisenberg-Kitaev model in a magnetic field, but by now applying the numerical technique of exact diagonalization for S = 1/2. Besides finding good agreement with our spin-wave calculations, we report possible evidence for a new quantum tricritical point.Nos últimos anos, a física do modelo de spin-1/2 de Kitaev na rede favo de mel e de suas generalizações tem atraído um enorme interesse, motivado pela busca pela compreensão de aspectos fundamentais e realizações experimentais de líquidos de spin quânticos. Um avanço notório nessa área foi a descoberta de que, quando aplicado em direções específicas, um campo magnético é capaz de induzir um líquido de spin topológico com gap no magneto quântico ∝-RuCl3. Em paralelo, a busca por outros materiais magnéticos com forte acoplamento spin-órbita resultou em propostas recentes de candidatos a realizar versões de spin-1 e spin-3/2 da interação de Kitaev. Notavelmente, a ausência de simetria de rotação de spin nesses sistemas induz processos de magnetização altamente anisotrópicos e novos estados magnéticos. Dado um contexto tão rico, esta dissertação tem como objetivo aprofundar o conhecimento dos efeitos de campo magnéticos em sistemas de Kitaev generalizados por meio de três contribuições. Primeiro, nós empregamos uma combinação de teoria de ondas de spin lineares e não-lineares para estudar as fases ordenadas induzidas por campos magnéticos no modelo Heisenberg-Kitaev, tipicamente tido como um modelo mínimo para descrever magnetismo de Kitaev para diferentes números quânticos de spin S. Com o desenvolvimento de uma expansão consistente em 1/S, nós analisamos a influência de flutuações quânticas de primeira ordem em observáveis físicos e nos diagramas de fases dos casos experimentalmente relevantes de S = 1/2, 1 e 3/2. Segundo, nós consideramos um modelo de spins mais realístico para descrever a resposta elástica a baixas temperaturas de ∝-RuCl3 em um campo magnético externo e sob pressão uniaxial pequena. Nossos resultados sugerem que aspectos anômalos encontrados em experimentos indicam a presença de um regime quântico a campos intermediários. Finalmente, retornamos ao modelo de Heisenberg-Kitaev em um campo magnético, porém agora empregando a técnica numérica de diagonalização exata para S = 1/2. Além de obter resultados em bom acordo com o nosso estudo de ondas de spin, nós reportamos possíveis evidências para um novo ponto tricrítico quântico.Biblioteca Digitais de Teses e Dissertações da USPAndrade, Eric de Castro eCônsoli, Pedro Monteiro2020-09-22info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisapplication/pdfhttps://www.teses.usp.br/teses/disponiveis/76/76131/tde-19112020-110752/reponame:Biblioteca Digital de Teses e Dissertações da USPinstname:Universidade de São Paulo (USP)instacron:USPLiberar o conteúdo para acesso público.info:eu-repo/semantics/openAccesseng2020-11-24T02:13:01Zoai:teses.usp.br:tde-19112020-110752Biblioteca Digital de Teses e Dissertaçõeshttp://www.teses.usp.br/PUBhttp://www.teses.usp.br/cgi-bin/mtd2br.plvirginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.bropendoar:27212020-11-24T02:13:01Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)false |
dc.title.none.fl_str_mv |
Extended Kitaev magnetism in magnetic fields Magnetismo de Kitaev estendido em campos magnéticos |
title |
Extended Kitaev magnetism in magnetic fields |
spellingShingle |
Extended Kitaev magnetism in magnetic fields Cônsoli, Pedro Monteiro Diagonalização exata Exact diagonalization Frustrated magnetism Heisenberg-Kitaev model Kitaev materials Magnetismo frustrado Materiais Kitaev Modelo de Heisenberg-Kitaev Spin-wave Theory Teoria de ondas de spin |
title_short |
Extended Kitaev magnetism in magnetic fields |
title_full |
Extended Kitaev magnetism in magnetic fields |
title_fullStr |
Extended Kitaev magnetism in magnetic fields |
title_full_unstemmed |
Extended Kitaev magnetism in magnetic fields |
title_sort |
Extended Kitaev magnetism in magnetic fields |
author |
Cônsoli, Pedro Monteiro |
author_facet |
Cônsoli, Pedro Monteiro |
author_role |
author |
dc.contributor.none.fl_str_mv |
Andrade, Eric de Castro e |
dc.contributor.author.fl_str_mv |
Cônsoli, Pedro Monteiro |
dc.subject.por.fl_str_mv |
Diagonalização exata Exact diagonalization Frustrated magnetism Heisenberg-Kitaev model Kitaev materials Magnetismo frustrado Materiais Kitaev Modelo de Heisenberg-Kitaev Spin-wave Theory Teoria de ondas de spin |
topic |
Diagonalização exata Exact diagonalization Frustrated magnetism Heisenberg-Kitaev model Kitaev materials Magnetismo frustrado Materiais Kitaev Modelo de Heisenberg-Kitaev Spin-wave Theory Teoria de ondas de spin |
description |
Over the past years, the physics of Kitaev\'s spin-1/2 honeycomb model and its extensions have attracted enormous interest, fueled by a pursuit of the fundamental understanding as well as experimental realizations of quantum spin-liquid phases. A notorious achievement in this field has been the discovery that, when applied in specific directions, a magnetic field can induce a gapped topological spin liquid in the Kitaev quantum magnet ∝-RuCl3. In parallel, the search for other magnets with strong spin-orbit coupling has resulted in recent proposals of material candidates to host spin-1 and spin-3/2 analogs of the Kitaev interaction. Remarkably, all of these materials display nontrivial responses to magnetic fields, such as strongly anisotropic magnetization processes and novel field-induced states, due to the lack of spin-rotational symmetry. Given such a rich background, this dissertation aims at expanding the current knowledge of the effects of magnetic fields on extended Kitaev systems with three different contributions. First, we employ a combination of linear and nonlinear spin-wave theory to study the ordered field-induced phases of the nearestneighbor Heisenberg-Kitaev model, which is often regarded as a minimal model to describe Kitaev magnetism for different spin quantum numbers S. By developing a consistent 1/S expansion, we analyze the influence of the leading-order quantum fluctuations on physical observables and phase diagrams of the experimentally relevant cases of S = 1/2, 1 and 3/2. Second, we consider a more realistic spin model to describe the low-temperature elastic response of ∝-RuCl3 in an applied magnetic field and small uniaxial pressure. Our results suggest that anomalous features found in experiments are indicative of an intermediate-field quantum paramagnetic regime. Finally, we return to the Heisenberg-Kitaev model in a magnetic field, but by now applying the numerical technique of exact diagonalization for S = 1/2. Besides finding good agreement with our spin-wave calculations, we report possible evidence for a new quantum tricritical point. |
publishDate |
2020 |
dc.date.none.fl_str_mv |
2020-09-22 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/masterThesis |
format |
masterThesis |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
https://www.teses.usp.br/teses/disponiveis/76/76131/tde-19112020-110752/ |
url |
https://www.teses.usp.br/teses/disponiveis/76/76131/tde-19112020-110752/ |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
|
dc.rights.driver.fl_str_mv |
Liberar o conteúdo para acesso público. info:eu-repo/semantics/openAccess |
rights_invalid_str_mv |
Liberar o conteúdo para acesso público. |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.coverage.none.fl_str_mv |
|
dc.publisher.none.fl_str_mv |
Biblioteca Digitais de Teses e Dissertações da USP |
publisher.none.fl_str_mv |
Biblioteca Digitais de Teses e Dissertações da USP |
dc.source.none.fl_str_mv |
reponame:Biblioteca Digital de Teses e Dissertações da USP instname:Universidade de São Paulo (USP) instacron:USP |
instname_str |
Universidade de São Paulo (USP) |
instacron_str |
USP |
institution |
USP |
reponame_str |
Biblioteca Digital de Teses e Dissertações da USP |
collection |
Biblioteca Digital de Teses e Dissertações da USP |
repository.name.fl_str_mv |
Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP) |
repository.mail.fl_str_mv |
virginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.br |
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1809090875558461440 |