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Doctoral Thesis
DOI
10.11606/T.76.2004.tde-09042008-103624
Document
Author
Full name
Vivaldo Leiria Campo Júnior
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2004
Supervisor
Committee
Oliveira, Luiz Nunes de (President)
Fóglio, Mário Eusébio
Ioriatti Junior, Liderio Citrangulo
Menezes, Jose Carlos Egues de
Silva, Antonio Jose Roque da
Title in Portuguese
O grupo de renormalização numérico e o problema de duas impurezas
Keywords in Portuguese
Assimetria partícula-buraco
Grupo de renormalização
Modelo de Anderson
Modelo de Kondo
Propriedades termodinâmicas
Abstract in Portuguese
Neste trabalho é calculada a contribuição de duas impurezas magnéticas ao calor específico e à entropia de um metal através do grupo de renormalização numérico. Tal sistema físico foi descrito pelo modelo Kondo de duas impurezas, onde cada impureza é simplesmente um momento magnético associado a um spin S=1/2, e representa um elétron ocupando um orbital de uma impureza magnética adicionada ao metal não magnético.Para tornar possível o cálculo com malhas de discretização grossas, foi introduzida uma correção no processo de discretização, levando a novas expressões para as energias da banda de condução discretizada e permitindo um melhor tratamento da assimetria partícula-buraco do modelo. Tal assimetria decorre da dependência com a energia do acoplamento entre as impurezas e os elétrons de condução do metal. A utilização de malhas grossas é extremamente desejável para a diminuição do esforço computacional envolvido.
Title in English
Numerical renormalization group and the two-impurity problem
Keywords in English
Anderson model
Kondo model
Particle-hole asymmetry
Renormalization group
Thermodynamic properties
Abstract in English
In this work the contribution of two magnetic impurities to the specific heat and the entropy of a metal through the group of numerical renormalization is calculated. Such physical system was described for the Kondo model of two impurities, where each impurity is simply an associated magnetic moment to one spin S=1/2, and represents an electron occupying a orbital one of a magnetic impurity added to the magnetic metal. To not become possible the calculation with thick meshes of discretization, was introduced a correction in the discretization process, having led the new expressions for the energies of the band of discredited conduction and allowing to one better treatment of the asymmetry particle-hole of the model. Such asymmetry elapses of the dependence with the energy of the coupling between the impurities and electrons of conduction of the metal. The use of thick meshes is extremely desirable for the reduction of the involved computational effort.
 
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Publishing Date
2008-04-17
 
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