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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Propriedades magnéticas do Modelo de Hubbard Clássico / MAGNETIC PROPERTIES OF HUBBARD MODEL CLASSIC.

Santos Filho, Adelino dos 19 July 2012 (has links)
In this work we obtain the magnetic and thermodynamic properties of the classical Hubbard model. This one is easier to handle than the original Hubbard model, and it maintains fundamental aspects like charge and particle-hole symmetry. We find the relationship between this and the Ising model. For square and simple cubic lattices, the thermodynamic properties and phase diagrams were calculated by Monte Carlo method. We show the behavior of internal energy, specific heat, and magnetic susceptibility as a function of the temperature. For the considered lattices, the ground state is anti-ferromagnetic. The Néel temperatures were found as a function of the electronic interaction in the case of half-filled band. In the limit of vanishing of diverging interaction, our results agree with the Ising model. / No presente trabalho, nós obtivemos as propriedades magnéticas e termodinâmicas do modelo clássico de Hubbard. Este é de mais fácil manipulação que o modelo original de Hubbard, e conserva aspectos fundamentais como a simetria partícula-buraco e de carga. Encontramos a relação entre este modelo e o de Ising. Para as redes quadrada e cúbica simples, as propriedades termodinâmicas e diagramas de fase foram calculadas através do método de Monte Carlo. Apresentamos o comportamento da energia interna, do calor específico e da susceptibilidade magnética como função da temperatura. Para as redes estudadas, o estado fundamental é antiferromagnético. As temperaturas de Néel foram encontradas como função da interação eletrônica no caso de banda meio-cheia. No limite de interação nula ou infinita, encontramos valores que concordam com o modelo de Ising.

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