First-order phase transition and anomalous hysteresis of Bose gases in optical lattices

TL;DR

This paper investigates first-order quantum phase transitions and a unique unidirectional hysteresis in Bose gases within optical lattices, revealing the phenomenon's ubiquity across various models and its underlying mechanisms.

Contribution

It demonstrates the occurrence of anomalous hysteresis in multiple Bose-Hubbard models and explains its mechanism using Ginzburg-Landau theory, highlighting its generality.

Findings

Anomalous hysteresis occurs in hardcore Bose-Hubbard models with dipole interactions.

The phenomenon is also present in two-component and spin-1 Bose-Hubbard models.

The hysteresis behavior is explained by the Ginzburg-Landau theory.

Abstract

We study the first-order quantum phase transitions of Bose gases in optical lattices. A special emphasis is placed on an anomalous hysteresis behavior, in which the phase transition occurs in a unidirectional way and a hysteresis loop does not form. We first revisit the hardcore Bose-Hubbard model with dipole-dipole interactions on a triangular lattice to analyze accurately the ground-state phase diagram and the hysteresis using the cluster mean-field theory combined with cluster-size scaling. Details of the anomalous hysteresis are presented. We next consider the two-component and spin-1 Bose-Hubbard models on a hypercubic lattice and show that the anomalous hysteresis can emerge in these systems as well. In particular, for the former model, we discuss the experimental feasibility of the first-order transitions and the associated hysteresis. We also explain an underlying mechanism of the anomalous hysteresis by means of the Ginzburg-Landau theory. From the given cases, we conclude that the anomalous hysteresis is a ubiquitous phenomenon of systems with a phase region of lobe shape that is surrounded by the first-order boundary.