Commensurate Two-Component Bosons in Optical Lattice: Groundstate Phase Diagram

TL;DR

This paper explores the complex phase diagram of two-component bosons in an optical lattice at commensurate filling, revealing multiple stable phases and phase transitions through a combination of quantum-to-classical mapping and Monte Carlo simulations.

Contribution

It introduces a novel mapping of the quantum system to a classical loop-current model and uncovers the presence of first-order transitions and multi-critical points in the phase diagram.

Findings

Identification of five stable groundstates including superfluid and insulating phases

Discovery of first-order transition and multi-critical points in the phase diagram

Explanation of first-order transitions using microscopic and mean-field arguments

Abstract

Two sorts of bosons in an optical lattice at commensurate filling factors can form five stable superfluid and insulating groundstates with rich and non-trivial phase diagram. The structure of the groundstate diagram is established by mapping $d$-dimensional quantum system onto a $(d+1)$-dimensional classical loop-current model and Monte Carlo simulations of the latter. Surprisingly, the quantum phase diagram features, besides second-order lines, a first-order transition and two multi-critical points. We explain why first-order transitions are generic for models with paring interactions using microscopic and mean-field arguments.