Competition between phase separation and "classical" intermediate valence in an exactly solved model

TL;DR

This paper provides an exact analysis of the spin-1/2 Falicov-Kimball model on an infinite-coordination Bethe lattice, revealing the competition between phase separation and classical intermediate valence, with implications for metal-insulator transitions.

Contribution

It offers the first exact solution showing how phase separation and intermediate valence compete, clarifying the nature of transitions in this model.

Findings

Phase separation or direct metal-insulator transition dominate large phase diagram regions.

Only continuous transitions occur within the intermediate valence phase.

Intermediate valence is suppressed by phase separation or first-order transitions.

Abstract

The exact solution of the spin-1/2 Falicov-Kimball model on an infinite-coordination Bethe lattice is analyzed in the regime of ``classical'' intermediate valence. We find (i) either phase separation or a direct metal-insulator transition preclude intermediate valence over a large portion of the phase diagram and (ii) within the intermediate valence phase, only continuous transitions are found as functions of the localized f-electron energy or temperature.