Susceptibilidade magnética de um modelo de Hubbard estendido com interação ao atrativa

• Autor(a) principal: Lobo, Cesar de Oliveira
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Manancial - Repositório Digital da UFSM
• dARK ID: ark:/26339/00130000095gp
• Texto Completo: http://repositorio.ufsm.br/handle/1/3904
• topic: Sistemas de elétrons fortemente correlacionados; Modelo de Hubbard; Funções de Green; Superfície de Fermi; Strong correlations; Hubbard model; Green s functions; Fermi surfaces; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA

Anomalous properties of the normal state of a strongly correlated electron system described by an attractive extended Hubbard model are investigated. The equations of motion of the Green s functions are calculated with the two-pole approximation which gives rise to quasiparticle renormalized bands. The two-pole approximation leads to a set of correlation functions. In particular, the antiferromagnetic correlation function h~Si · ~Sji plays an important role as a source of anomalies in the normal state of the model. The uniform static magnetic susceptibility as a function of occupation nT and temperature is calculated. At low temperatures, the susceptibility presents a peak for nT ≃ 0.80. The results suggest that it is the onset of short range antiferromagnetic correlations, which could be a mechanism for the pseudogap. The Fermi surface, defined by the spectral function A(ω = 0,~k), is presented for different dopings. It has been observed that above nT ≃ 0.80 the ordinary Fermi surface evolves to a hole-pocket with pseudogaps near the antinodal points (0, π) and (π, 0).