Effective-action approach to dirty bosons in optical lattices

Detalhes bibliográficos
Ano de defesa: 2019
Autor(a) principal: Souza, Renan da Silva
Orientador(a): Santos, Francisco Ednilson Alves dos lattes
Banca de defesa: Não Informado pela instituição
Tipo de documento: Dissertação
Tipo de acesso: Acesso aberto
Idioma: eng
Instituição de defesa: Universidade Federal de São Carlos
Câmpus São Carlos
Programa de Pós-Graduação: Programa de Pós-Graduação em Física - PPGF
Departamento: Não Informado pela instituição
País: Não Informado pela instituição
Palavras-chave em Português:
Palavras-chave em Inglês:
Área do conhecimento CNPq:
Link de acesso: https://repositorio.ufscar.br/handle/20.500.14289/11449
Resumo: A system of cold bosonic atoms loaded in an optical lattice potential can undergo a macroscopic phase transition due to quantum fluctuations. As the depth of the lattice potential is increased, the ground state of the many-body system is found to go from a superfluid to a Mott-insulator state. In the presence of disorder a new phase intervenes in these transition: the Bose-glass phase. Usual analysis of this phase transition is made within the framework of mean-field theory. Such approximation predicts non-physical results for the condensate density. Taking into consideration the lack of precise analytical results in the literature, we propose the use of an effective-action approach for investigating such phase transition in the presence of disorder at arbitrary temperatures. These method, based on standard field-theoretical considerations, is used with the aim to improve the results of former analytical methods and provide better qualitative understanding of the quantum phase transition. We considered static diagonal disorder by means of a local chemical potential in the Bose-Hubbard model and obtained the phase boundary for homogeneous and Gaussian disorder distributions. We compared the condensate density predictions of our field theoretical effective-action method with the results of standard mean-field approximation. The application of the effective-action method showed to be promising in analyzing the superfluid to insulating states phase transition in the presence of disorder as well as in improving former analytical results.