Band to Mott Insulator Transition in the Ionic Hubbard Model

A. Baldwin, Richard T. Scalettar, Norman Paris

Ara Go, Gun Sang Jeon

Marcin M. Wysokiński

The ionic Hubbard model is a paradigmatic setup for studying the competition between band and Mott insulating behavior. Within the variationally exact in infinite dimensions Gutzwiller approximation, we derive a compact analytic expression for the phase boundary between the Mott and band insulators. While the method reproduces the expected band–Mott insulator phenomenology, it does not capture the correlated metallic state at finite staggered potential found, for example, in dynamical mean-field theory. This absence highlights that the metallic phase originates from incoherent Hubbard-band physics rather than Fermi-liquid behavior well captured by the Gutzwiller approximation. Our formulation establishes a concise variational framework for the ionic Hubbard model, with natural extensions to nonequilibrium setups and spin-exchange dynamics. Abstract Published by the Jagiellonian University 2026 authors

R. Bulla, Thomas Pruschke, Alex C. Hewson

Duc‐Anh Le, Anh-Tuan Hoang

We study electronic phase transitions in the half-filled ionic Hubbard model with an on-site Coulomb repulsion U and an ionic energy Δ by using the Kotliar–Ruckenstein slave-boson theory. Assuming a paramagnetic solution, we show that for any non-zero values of Δ, with increasing U the system undergoes a transition from band-insulator to Mott-insulator. Our results have implied the absence of a metallic phase between the band and the Mott insulator phases.

L. Tincani, R. M. Noack, D. Baeriswyl

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.