Magnetic phases and transitions of the two-species Bose-Hubbard model

TL;DR

This paper investigates the magnetic phases and phase transitions in a two-species Bose-Hubbard model at finite temperature, combining Landau theory and a field-theoretical approach to map out the phase diagram and critical phenomena.

Contribution

It introduces a comprehensive analysis of magnetic order and phase transitions in the two-species Bose-Hubbard model, highlighting the role of particle-number fluctuations and first-order transitions.

Findings

First-order transitions and hysteresis near multicritical points.

Maximum transition temperature limited by superfluid phase.

Explicit thermodynamic phase diagram including fluctuations.

Abstract

A model of two-species bosons moving on the sites of a lattice is studied at nonzero temperature, focusing on magnetic order and superfluid-insulator transitions. Firstly, Landau theory is used to find the general structure of the phase diagram, and in particular to demonstrate the presence of first-order transitions and hysteresis in the vicinity of a multicritical point. Secondly, an explicit thermodynamic phase diagram is calculated using an approach based on a field-theoretical description of the Bose-Hubbard model, which incorporates the crucial effects of particle-number fluctuations. The maximum transition temperature to a magnetically ordered Mott insulator is found to be limited by the presence of the superfluid phase.