Magnetic Phase Transition in the Ground-State Phase Diagram of Binary Bose Gases in Optical Lattices

TL;DR

This study uses quantum Monte Carlo simulations to explore the magnetic phase transitions in binary Bose gases within optical lattices, revealing a transition from ferromagnetic order to a spin insulator and its dependence on interaction parameters.

Contribution

It provides the first detailed quantum Monte Carlo analysis of magnetic phase transitions in binary Bose gases in optical lattices, highlighting the nature and merging of phase transitions.

Findings

Identified a magnetic phase transition within the Mott insulator phase.

Characterized the transition as a 3D-XY type with ferromagnetic correlations.

Showed the transition merges with the Mott-superfluid transition at lower interspecies interactions.

Abstract

We investigate the ground-state phase diagram of interacting binary Bose gases trapped in two-dimensional optical lattices by means of quantum Monte Carlo simulations. Our simulations reveal a magnetic phase transition from a $x-y$ ferromagnetic-order to a spin insulator inside the Mott insulating phase with two particles per site for quasi-balanced on-site inter- and intra-particle interactions, i.e., $U_{\uparrow \downarrow} \lesssim U$. This 3D-XY transition is characterized by the establishment of a finite local magnetic moment along the $z$-axis, ferromagnetic correlations in the $x-y$ plan and by counterflow superfluidity inside the Mott phase. When decreasing $U_{\uparrow \downarrow}/U$, this transition merges with the Mott-superfluid transition and becomes first-order. The merging of the two transitions is investigated with respect to $U_{\uparrow \downarrow}/U$ parameter.