Mott transitions in the Hubbard model with spatially-modulated interactions

TL;DR

This paper investigates the effects of spatially modulated interactions in the Hubbard model, revealing various phases such as magnetically ordered, superfluid, and metal-insulator transitions using dynamical mean-field theory.

Contribution

It introduces a detailed analysis of the Hubbard model with alternating on-site interactions, highlighting the interplay between repulsive and attractive interactions and their impact on phase transitions.

Findings

Magnetically ordered state at half-filling with repulsive interactions

Superfluid state with particle imbalance in the attractive case

Metal-insulator transition occurs when repulsive and attractive interactions are comparable

Abstract

We study two-component fermions in optical lattices with spatially alternating on-site interactions using dynamical mean-field theory. Calculating the quasi-particle weight, double occupancy, and order parameters for each sublattice, we discuss the low-temperature properties of the system. When both interactions are repulsive, the magnetically ordered state is realized at half-filling. In the attractive case, the superfluid state is, in general, realized with a particle number imbalance. On the other hand, when repulsive and attractive interactions are comparable in the half-filled system, the magnetically ordered and superfluid states are not realized, but the metal-insulator transition occurs. This transition is characterized by the Mott and pairing transitions discussed in the conventional repulsive and attractive Hubbard models. In the doped system, commensurability emerges owing to the repulsive interactions and the metal-insulator transition occurs down to quarter-filling.