MÉTODO RPA RENORMALIZADO PARA O MODELO DE HUBBARD ESTENDIDO / RENORMALIZED RPA METHOD FOR THE EXTENDED HUBBARD MODEL
AUTOR(ES)
LOURIVAL MANOEL DA SILVA FILHO
DATA DE PUBLICAÇÃO
2003
RESUMO
In this work we apply the Random Phase Approximation (RPA) to the Extended Hubbard Model in one dimension. Initially we investigate the e®ect of the first neighbor interaction term, V , on the spin and charge susceptibilities. When V is small, its influence is also very small but as it grows, it tends to lower the plasmon frequency and to inhibit the condition for the existence of magnons. We also have calculated numerically both the spin and the charge susceptibilities for U = 3,4 and 5 with V in the region (0; U). Starting from the SDW region and increasing V we found that the plasmon peak in the charge susceptibility for 2kF tends to ! = 0, indicating an instability against the formation of a CDW ground state. This allows us to determine the phase separation line between the two phases. According to the conventional RPA, this transition occurs for U = 2V but due to the renormalization process, we nd that this frontier shifts slightly to the interior of the CDW region, in agreement with methods not using the mean eld approximation.
ASSUNTO(S)
modelo de hubbard estendido extended hubbard model rpa rpa renormalizado renormalized rpa rpa
