Phase diagram of the ionic Hubbard model with density-dependent hopping

TL;DR

This paper maps the phase diagram of an ionic Hubbard model with density-dependent hopping, revealing topological phase transitions and the expansion of the dimerized insulator phase, relevant for cold atom experiments.

Contribution

It introduces a detailed quantum phase diagram for the ionic Hubbard model with density-dependent hopping, highlighting topological phase boundaries and the effects of hopping modifications.

Findings

Topological charge and spin Berry phase jumps mark phase boundaries.

The dimerized insulator phase expands with reduced non-alternating hopping.

Results are relevant for cold atom experiments observing topological charge pumping.

Abstract

We obtain the quantum phase diagram of the ionic Hubbard model including electron-hole symmetric density-dependent hopping. The boundaries of the phases are determined by crossing of excited levels with particular discrete symmetries, which coincide with jumps of charge and spin Berry phases with a topological meaning. Reducing the magnitude of the hopping terms that do not change the total number of singly occupied sites with respect to the other one, the region of the phase diagram occupied by the fully gapped spontaneously dimerized insulator (which separates the band insulating and Mott insulating phases) is enlarged, particularly for small values of the alternating on-site energy. This result might be relevant for experiments in cold atoms in which topological charge pumping is observed when alternation in the hopping is included.