Os seminários nesta quarta feira dia 03/07/2013 serão no AUDITÓRIO DA FÍSICA as 10h.
Leticia
SEMINÁRIO 01: COESÃO GEOMÉTRICA EM MATERIAIS GRANULARES .
MINISTRANTE: Maycon Silva Santos
DATA: 03/07/2013 LOCAL: Auditório da Física / CCN HORÁRIO: 10:00 h
Neste seminário vamos tratar de um estudo rápido sobre, coesão geométrica em materiais granulares. Será feita uma breve abordagem histórica sobre este trabalho e mostraremos alguns resultados obtidos, dentro desse contexto também falaremos de forma bem simplória sobre leis de escalas e fenômenos de não-equilíbrio,com uma atenção especial no trabalho de empilhamento.
SEMINÁRIO 02: A MEAN-FIELD APPROACH TO THE KONDO--ATTRACTIVE-HUBBARD MODEL
MINISTRANTE: Natanael de Carvalho Costa
DATA: 03/07/2013 LOCAL: Auditório da Física / CCN HORÁRIO: 11:00 h
Over the past few decades, coexistence between superconductivity and magnetic order has been found in a variety of families of materials, such as heavy fermions, borocarbides, and, more recently, in iron pnictides and some cuprates.
However, a microscopic description of this coexistence is still in its infancy. An interesting class of materials showing this coexistence comprises of the borocarbides, which contain a rare-earth element in their chemical composition. The rare-earth element provides a local magnetic moment that interacts with the conduction electrons, which, in turn, are subject to a phonon-mediated pairing interaction.
In order to model these materials, Bertussi et al. considered a local on-site attraction for the conduction electrons, while their coupling with the local magnetic moments is described by a Kondo term. Their the Hamiltonian is taken as the joint of a term of Kondo lattice with a term of attractive Hubbard. The one-dimensional version of the model was investigated through density-matrix renormalization group (DMRG), from which a ground state phase diagram was established, showing regions of coexistence of superconductivity and spin-density waves; these results are in qualitative agreement with the trend observed in borocarbides.
In the present work, we consider this model in 2D, within the Hartree-Fock approximation. We will discuss results for the superconducting gap, for the magnetizations for the conduction electrons and local moments. From these results, we extract a phase diagram (T=0), from which regions of coexistence between superconductivity and magnetism are mapped out. The results are compared with experimental data.
