Phys. Rev. B 54
, 7771-7778 (1996)
Metal-Insulator Transitions Due to Self-doping
S. Blawid, H. A. Tuan, T. Yanagisawa, P. Fulde
We investigate the influence of an unoccupied band on the transport properties of a strongly correlated electron system. For that purpose, additional orbitals are coupled to a Hubbard model via hybridization. The filling is one electron per site. Depending on the position of the additional band, both a metal-to-insulator and an insulator-to-metal transition occur with increasing hybridization. The latter transition from a Mott insulator into a metal via ''self-doping'' was recently proposed to explain the low carrier concentration in Yb4As3. We suggest a restrictive parameter regime for this transition, making use of exact results-in various limits. The predicted absence of the self-doping transition for nested Fermi surfaces is confirmed by means of an unrestricted Hartree-Fock approximation and an exact diagonalization study in one dimension. Ln the general case metal-insulator phase diagrams are obtained within the slave-boson mean-field and the alloy-analog approximations.