Finite temperature phase diagram of spin-1/2 bosons in two-dimensional optical lattice

TL;DR

This paper investigates the finite temperature phase diagram of a two-species spin-1/2 bosonic Hubbard model on a 2D lattice, revealing various phases and phase transitions through quantum Monte Carlo simulations.

Contribution

It provides the first detailed finite temperature phase diagram for this model, highlighting the effects of ferromagnetic and antiferromagnetic interactions.

Findings

Identification of solid, liquid, and superfluid phases.

Polarization of superfluid in antiferromagnetic case.

Berezinsky-Kosterlitz-Thouless transition for superfluid-liquid transition.

Abstract

We study a two-species bosonic Hubbard model on a two-dimensional square lattice by means of quantum Monte Carlo simulations and focus on finite temperature effects. We show in two different cases, ferro- and antiferromagnetic spin-spin interactions, that the phase diagram is composed of solid Mott phases, liquid phases and superfluid phases. In the antiferromagnetic case, the superfluid (SF) is polarized while the Mott insulator (MI) and normal Bose liquid (NBL) phases are not. On the other hand, in the ferromagnetic case, none of the phases is polarized. The superfluid-liquid transition is of the Berezinsky-Kosterlitz-Thouless type whereas the solid-liquid passage is a crossover.