Finite-temperature phase transitions in the ionic Hubbard model

TL;DR

This paper studies how the ionic Hubbard model in infinite dimensions undergoes temperature-dependent phase transitions, revealing a crossover from band insulator to metal and then to Mott insulator, with the metallic phase being a Fermi liquid.

Contribution

It provides the first finite-temperature phase diagram of the ionic Hubbard model using dynamical mean-field theory and continuous-time quantum Monte Carlo methods.

Findings

Crossover from band insulator to metal with increasing interaction.

First-order transition from metal to Mott insulator at low temperatures.

Metallic phase remains stable against strong staggered potentials at low temperatures.

Abstract

We investigate paramagnetic metal-insulator transitions in the infinite-dimensional ionic Hubbard model at finite temperatures. By means of the dynamical mean-field theory with an impurity solver of the continuous-time quantum Monte Carlo method, we show that an increase in the interaction strength brings about a crossover from a band insulating phase to a metallic one, followed by a first-order transition to a Mott insulating phase. The first-order transition turns into a crossover above a certain critical temperature, which becomes higher as the staggered lattice potential is increased. Further, analysis of the temperature dependence of the energy density discloses that the intermediate metallic phase is a Fermi liquid. It is also found that the metallic phase is stable against strong staggered potentials even at very low temperatures.