Exact eigenstates for a Hamiltonian which represents a first order perturbative approximation of the periodic Anderson model

Abstract

AbstractWe consider a two‐band model with strong correlations derived from the Periodic Anderson Model by means of first order perturbation theory with respect to 1/U (U is the local interaction for f‐sites). We show that at half‐filling the Gutzwiller ansatz is an exact solution of that model for special parameters, generalizing a result of Brand and Giesekus. We use an exponential representation of the wave function, which allows for the derivations to use a terminating multi‐commutator expansion. The latter motivates a generaliztion of the Gutzwiller wave function for the half‐filled case. The combination of the Bardeen Cooper Schrieffer wave function and the Gutzwiller ansatz leads to exact solutions for further two‐band models with strong correlations.