Pseudogap e calor específico de um modelo de hubbard repulsivo
Autor(a) principal: | |
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Data de Publicação: | 2014 |
Tipo de documento: | Dissertação |
Idioma: | por |
Título da fonte: | Repositório Institucional Manancial UFSM |
Texto Completo: | http://repositorio.ufsm.br/handle/1/9244 |
Resumo: | The specific heat and the condensation energy of a two-dimensional Hubbard model, suitable to discuss high Tc superconductors (HTSTC), is studied taking into account hopping to first (t) and second (t2) nearest neighbors. Results for the Hubbard model show that the specific heat as a function of the temperature C(T) presents a two peaks structure (DUFFY; MOREO, 1997). The low temperature peak has been associated with spin fluctuation while the high temperature peak is related to charge fluctuation. Experimental results for the specific heat of HTSC s (LORAM et al., 2001), for instance, the YBCO and LSCO, indicate a close relation between the pseudogap and the specific heat. In the present work, we investigate the specific heat by the Green s function method within the n-pole approximation proposed by L. Roth (ROTH, 1969). The specific heat is calculated on the pseudogap and on the superconducting regions. Superconductivity with dx2−y2- wave pairing is considered following the procedure proposed by Beenen and Edwards (BEENEN; EDWARDS, 1995). The analytical expressions for the specific heat and for the condensation energy have been obtained following the formalism presented in reference (KISHORE; JOSHI, 1971). In the present scenario, the pseudogap emerges when the antiferromagnetic (AF) fluctuations (present in the Roth s band shift) become strongly sufficient to push down the region of the nodal point (π,π) on the renormalized quasi-particle bands. We observed that above a given total occupation nT , the specific heat decreases signaling the pseudogap presence. The effects of the antiferromagnetic fluctuations on the condensation energy and on superconductivity are also investigated.x |
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2017-05-022017-05-022014-08-15LAUSMANN, Ana Claudia. Pseudogap and the specific heat respulsive hubbard model. 2014. 73 f. Dissertação (Mestrado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2014.http://repositorio.ufsm.br/handle/1/9244The specific heat and the condensation energy of a two-dimensional Hubbard model, suitable to discuss high Tc superconductors (HTSTC), is studied taking into account hopping to first (t) and second (t2) nearest neighbors. Results for the Hubbard model show that the specific heat as a function of the temperature C(T) presents a two peaks structure (DUFFY; MOREO, 1997). The low temperature peak has been associated with spin fluctuation while the high temperature peak is related to charge fluctuation. Experimental results for the specific heat of HTSC s (LORAM et al., 2001), for instance, the YBCO and LSCO, indicate a close relation between the pseudogap and the specific heat. In the present work, we investigate the specific heat by the Green s function method within the n-pole approximation proposed by L. Roth (ROTH, 1969). The specific heat is calculated on the pseudogap and on the superconducting regions. Superconductivity with dx2−y2- wave pairing is considered following the procedure proposed by Beenen and Edwards (BEENEN; EDWARDS, 1995). The analytical expressions for the specific heat and for the condensation energy have been obtained following the formalism presented in reference (KISHORE; JOSHI, 1971). In the present scenario, the pseudogap emerges when the antiferromagnetic (AF) fluctuations (present in the Roth s band shift) become strongly sufficient to push down the region of the nodal point (π,π) on the renormalized quasi-particle bands. We observed that above a given total occupation nT , the specific heat decreases signaling the pseudogap presence. The effects of the antiferromagnetic fluctuations on the condensation energy and on superconductivity are also investigated.xNo presente trabalho estuda-se o calor específico de um modelo de Hubbard considerado adequado para discutir supercondutores de altas temperaturas. Resultados para o modelo de Hubbard mostram que o calor específico em função da temperatura apresenta uma estrutura de dois picos (DUFFY; MOREO, 1997). O pico de baixa temperatura está associado às flutuações de spin, enquanto que o pico em alta temperatura está relacionado às flutuações de carga. Por outro lado, resultados experimentais do calor específico de supercondutores de altas temperaturas (LORAM et al., 2001), como por exemplo o Y BCO e o LSCO, indicam uma forte relação entre o calor específico e o pseudogap. Portanto, neste trabalho investiga-se a relação entre o pseudogap e o calor específico de um modelo de Hubbard usando a técnica das funções de Green em conjunto com a aproximação de n-pólos proposta por L. Roth (ROTH, 1969). O calor específico é calculado na região do pseudogap e da supercondutividade. Considera-se supercondutividade com simetria de onda dx2 − y2 e o parâmetro de ordem supercondutor é obtido seguindo-se o procedimento de fatorização proposto por Beenen e Edwards (BEENEN; EDWARDS, 1995). A expressão analítica do calor específico é obtida seguindo o formalismo proposto na referência (KISHORE; JOSHI, 1971). No cenário adotado, o pseudogap emerge quando flutuações antiferromagnéticas, as quais estão relacionadas a correlações antiferromagnéticas (presentes no deslocamento de banda da Roth), tornam-se fortes o suficiente para puxar as bandas renormalizadas para energias abaixo do potencial químico no ponto (π,π). Observou-se que acima de uma certa ocupação, o salto no calor específico decresce sinalizando a abertura do pseudogap. Os efeitos das flutuações antiferromagnéticas sobre a energia de condensação e sobre a supercondutividade também são investigados.Conselho Nacional de Desenvolvimento Científico e Tecnológicoapplication/pdfporUniversidade Federal de Santa MariaPrograma de Pós-Graduação em FísicaUFSMBRFísicaModelo de HubbardPseudogapFunções de GreenCalor específicoFlutuações antiferromagnéticasHubbard modelPseudogapGreen s functionsSpecific heatAntiferromagnetic fluctuationsCNPQ::CIENCIAS EXATAS E DA TERRA::FISICAPseudogap e calor específico de um modelo de hubbard repulsivoPseudogap and the specific heat respulsive hubbard modelinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisCalegari, Eleonir Joãohttp://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4765559T0Troper, Amoshttp://lattes.cnpq.br/9920646475671338Chaves, Carlos Mauricio Giesbrecht Ferreirahttp://lattes.cnpq.br/5695533520447743http://lattes.cnpq.br/5060865206805722Lausmann, Ana Claudia100500000006400500300500500d7e676e6-ef5f-4dac-af83-a1a38f4b59cac65a5de8-0fcc-4555-a613-56c664bbb13491f6a2f0-bb16-44cf-8a6b-4cb3d0352e7a2231e4fe-69e1-48c1-b80c-ebb5b4a0c1e9info:eu-repo/semantics/openAccessreponame:Repositório Institucional Manancial UFSMinstname:Universidade Federal de Santa Maria (UFSM)instacron:UFSMORIGINALLAUSMANN, ANA CLAUDIA.pdfapplication/pdf7809946http://repositorio.ufsm.br/bitstream/1/9244/1/LAUSMANN%2c%20ANA%20CLAUDIA.pdf8f443b95bc0d28f974f16242dc3aa7f2MD51TEXTLAUSMANN, ANA CLAUDIA.pdf.txtLAUSMANN, ANA CLAUDIA.pdf.txtExtracted texttext/plain123720http://repositorio.ufsm.br/bitstream/1/9244/2/LAUSMANN%2c%20ANA%20CLAUDIA.pdf.txt3925c4a59218a73d61537ed4bf1364f9MD52THUMBNAILLAUSMANN, ANA CLAUDIA.pdf.jpgLAUSMANN, ANA CLAUDIA.pdf.jpgIM Thumbnailimage/jpeg4731http://repositorio.ufsm.br/bitstream/1/9244/3/LAUSMANN%2c%20ANA%20CLAUDIA.pdf.jpgf5a52d1cef5420962d8bad06d9e609c7MD531/92442022-07-05 09:50:30.845oai:repositorio.ufsm.br:1/9244Repositório Institucionalhttp://repositorio.ufsm.br/PUBhttp://repositorio.ufsm.br/oai/requestouvidoria@ufsm.bropendoar:39132022-07-05T12:50:30Repositório Institucional Manancial UFSM - Universidade Federal de Santa Maria (UFSM)false |
dc.title.por.fl_str_mv |
Pseudogap e calor específico de um modelo de hubbard repulsivo |
dc.title.alternative.eng.fl_str_mv |
Pseudogap and the specific heat respulsive hubbard model |
title |
Pseudogap e calor específico de um modelo de hubbard repulsivo |
spellingShingle |
Pseudogap e calor específico de um modelo de hubbard repulsivo Lausmann, Ana Claudia Modelo de Hubbard Pseudogap Funções de Green Calor específico Flutuações antiferromagnéticas Hubbard model Pseudogap Green s functions Specific heat Antiferromagnetic fluctuations CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
title_short |
Pseudogap e calor específico de um modelo de hubbard repulsivo |
title_full |
Pseudogap e calor específico de um modelo de hubbard repulsivo |
title_fullStr |
Pseudogap e calor específico de um modelo de hubbard repulsivo |
title_full_unstemmed |
Pseudogap e calor específico de um modelo de hubbard repulsivo |
title_sort |
Pseudogap e calor específico de um modelo de hubbard repulsivo |
author |
Lausmann, Ana Claudia |
author_facet |
Lausmann, Ana Claudia |
author_role |
author |
dc.contributor.advisor1.fl_str_mv |
Calegari, Eleonir João |
dc.contributor.advisor1Lattes.fl_str_mv |
http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4765559T0 |
dc.contributor.referee1.fl_str_mv |
Troper, Amos |
dc.contributor.referee1Lattes.fl_str_mv |
http://lattes.cnpq.br/9920646475671338 |
dc.contributor.referee2.fl_str_mv |
Chaves, Carlos Mauricio Giesbrecht Ferreira |
dc.contributor.referee2Lattes.fl_str_mv |
http://lattes.cnpq.br/5695533520447743 |
dc.contributor.authorLattes.fl_str_mv |
http://lattes.cnpq.br/5060865206805722 |
dc.contributor.author.fl_str_mv |
Lausmann, Ana Claudia |
contributor_str_mv |
Calegari, Eleonir João Troper, Amos Chaves, Carlos Mauricio Giesbrecht Ferreira |
dc.subject.por.fl_str_mv |
Modelo de Hubbard Pseudogap Funções de Green Calor específico Flutuações antiferromagnéticas |
topic |
Modelo de Hubbard Pseudogap Funções de Green Calor específico Flutuações antiferromagnéticas Hubbard model Pseudogap Green s functions Specific heat Antiferromagnetic fluctuations CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
dc.subject.eng.fl_str_mv |
Hubbard model Pseudogap Green s functions Specific heat Antiferromagnetic fluctuations |
dc.subject.cnpq.fl_str_mv |
CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
description |
The specific heat and the condensation energy of a two-dimensional Hubbard model, suitable to discuss high Tc superconductors (HTSTC), is studied taking into account hopping to first (t) and second (t2) nearest neighbors. Results for the Hubbard model show that the specific heat as a function of the temperature C(T) presents a two peaks structure (DUFFY; MOREO, 1997). The low temperature peak has been associated with spin fluctuation while the high temperature peak is related to charge fluctuation. Experimental results for the specific heat of HTSC s (LORAM et al., 2001), for instance, the YBCO and LSCO, indicate a close relation between the pseudogap and the specific heat. In the present work, we investigate the specific heat by the Green s function method within the n-pole approximation proposed by L. Roth (ROTH, 1969). The specific heat is calculated on the pseudogap and on the superconducting regions. Superconductivity with dx2−y2- wave pairing is considered following the procedure proposed by Beenen and Edwards (BEENEN; EDWARDS, 1995). The analytical expressions for the specific heat and for the condensation energy have been obtained following the formalism presented in reference (KISHORE; JOSHI, 1971). In the present scenario, the pseudogap emerges when the antiferromagnetic (AF) fluctuations (present in the Roth s band shift) become strongly sufficient to push down the region of the nodal point (π,π) on the renormalized quasi-particle bands. We observed that above a given total occupation nT , the specific heat decreases signaling the pseudogap presence. The effects of the antiferromagnetic fluctuations on the condensation energy and on superconductivity are also investigated.x |
publishDate |
2014 |
dc.date.issued.fl_str_mv |
2014-08-15 |
dc.date.accessioned.fl_str_mv |
2017-05-02 |
dc.date.available.fl_str_mv |
2017-05-02 |
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.citation.fl_str_mv |
LAUSMANN, Ana Claudia. Pseudogap and the specific heat respulsive hubbard model. 2014. 73 f. Dissertação (Mestrado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2014. |
dc.identifier.uri.fl_str_mv |
http://repositorio.ufsm.br/handle/1/9244 |
identifier_str_mv |
LAUSMANN, Ana Claudia. Pseudogap and the specific heat respulsive hubbard model. 2014. 73 f. Dissertação (Mestrado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2014. |
url |
http://repositorio.ufsm.br/handle/1/9244 |
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por |
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por |
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100500000006 |
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info:eu-repo/semantics/openAccess |
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openAccess |
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application/pdf |
dc.publisher.none.fl_str_mv |
Universidade Federal de Santa Maria |
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Programa de Pós-Graduação em Física |
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UFSM |
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BR |
dc.publisher.department.fl_str_mv |
Física |
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Universidade Federal de Santa Maria |
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