Critical properties of the band-insulator-to-Mott-insulator transition in the strong-coupling limit of the ionic Hubbard model

TL;DR

This study analyzes the phase transitions in a one-dimensional ionic Hubbard model using a strong-coupling effective approach, revealing Ising and Kosterlitz-Thouless transitions consistent with theoretical predictions.

Contribution

It provides a detailed finite-size scaling analysis of the ionic Hubbard model, identifying the nature of two key phase transitions in the strong-coupling limit.

Findings

The transition from band-insulating to dimerized phase is Ising.

The transition from dimerized to Mott-insulating phase is Kosterlitz-Thouless.

Results agree with field-theory predictions.

Abstract

We investigate the neutral-to-ionic insulator-insulator transition in one-dimensional materials by treating a strong-coupling effective model based on the ionic Hubbard model using the density-matrix renormalization group and finite-size scaling. The effective model, formulated in a spin-one representation, contains a single parameter. We carry out an extensive finite-size scaling analysis of the relevant gaps and susceptibilities to characterize the two zero-temperature transitions. We find that the transition from the ionic band-insulating phase to an intermediate spontaneously dimerized phase is Ising, and the transition from the dimerized phase to the Mott-insulating phase is Kosterlitz-Thouless, in agreement with the field-theory-based predictions.