Mean-field ground-state phase diagram of the ${t-t^\prime}$ ionic-Hubbard chain

TL;DR

This paper maps the ground-state phase diagram of a one-dimensional ionic-Hubbard model with extended hopping, revealing complex insulating phases and topological transitions influenced by interactions and lattice modulations.

Contribution

It provides a mean-field analysis of the phase diagram including the effects of next-nearest neighbor hopping and topological Lifshitz transition, which was not previously detailed.

Findings

Insulating phases with charge and antiferromagnetic order dominate the phase diagram.

Emergence of charge- and spin-density modulations after the Lifshitz transition.

Different coexistence regimes of charge, spin, and ferrimagnetic order depending on interaction strength.

Abstract

Ground state (GS) phase diagram of the one dimensional repulsive Hubbard model with both nearest neighbor ($t$) and next-nearest-neighbor ($t^{\prime}$) hopping and a staggered potential ($\Delta$) is determined in the case of half-filled band and zero net magnetization within the mean-field theory. The model may be realized by cold atoms in engineered optical lattices. Connection between the peculiarities of the GS phase diagram of the interacting system and the topological Lifshitz transition in GS of free particle chain is discussed. The mean-field Hamiltonian is given by six order parameters, which are determined self-consistently. It is shown that the GS phase diagram {\em predominantly} consists of insulating phases characterized by coexistence of the long-range ordered modulations of the charge- (I) and antiferromagnetic (AF) spin-density with wavelengths equal to two and/or four lattice units. Below the Lifshitz transition, the GS phase diagram is qualitatively similar to that of the standard (${t^{\prime}=0}$) ionic Hubbard model. After the Lifshitz transition, charge- and spin-density modulations emerge within the sublattices and have wavelengths equal to four lattice units. For moderate values of the on-site repulsion the insulating phases are characterized by the presence of I and AF modulations coexisting with ferrimagnetic spin- and charge-density modulations within the one sublattice, or by the coexistence of I order and additional AF spin density modulation only within the sublattice with high ionic potential. At large repulsion the insulating phase with AF order inside both sublattices and remaining small ionicity left between the sublattices is realized.