Spectral density for the Anderson\'s Model of two impurities.

Author(s)

Cíntia Aguiar de Paula

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 1998-03-30

Examining board members

Luiz Nunes de Oliveira; José Roberto Iglesias; Lidério Citrangulo Ioriatti Junior; Gilmar Eugenio Marques; Eduardo Miranda

• Advisor: Luiz Nunes de Oliveira

Abstract

We calculated the spectral density for the two-impurity Anderson model by means of an extension of the numerical renormalization-group (NRG) preserving the particle-hole asymmetry of the model. The ground state of this model depends strongly on the competition between the RKKY interaction I and the Kondo temperature TK. That competition generates three characteristic regimes: (i) 11\\« kBTK, Kondo regime; (ii) - I» kBTK, ferromagnetic regime; and (iii) I > > k B TK, antiferromagnetic regime. The Hamiltonian is invariant under inversion of the impurity coordinates ± R/2 . Its eigenstates can therefare be classified according to parity. We have calculated the even and odd spectral densities for model parameters representative of each of the three above mentioned regimes. Various features af the numerical results, associated with the formation of an impurity singlet ar triplet and with the Kondo effect, are discussed. (AU)