Metal-insulator crossover in the Boson-Fermion model in infinite dimensions

TL;DR

This paper investigates how strong pair fluctuations in the Boson-Fermion model cause a metal-insulator crossover in infinite dimensions, characterized by pseudogap formation and changes in conductivity.

Contribution

It demonstrates the occurrence of a temperature-driven metal-insulator crossover due to pair fluctuations within the Boson-Fermion model using dynamical mean field theory.

Findings

Pseudogap opens in the density of states at low temperatures

Optical and dc conductivity show signatures of crossover

Strong pair fluctuations drive the metal-insulator transition

Abstract

The Boson-Fermion model, describing a mixture of tightly bound electron pairs and quasi-free electrons hybridized with each other via a charge exchange term, is studied in the limit of infinite dimensions, using the Non-Crossing Approximation within the Dynamical Mean Field Theory. It is shown that a metal-insulator crossover, driven by strong pair fluctuations, takes place as the temperature is lowered. It manifests itself in the opening of a pseudogap in the electron density of states, accompanied by a corresponding effect in the optical and dc conductivity.