# Phase transitions of the coherently coupled two-component Bose gas in a square optical lattice

## TL;DR

This paper explores how coherent coupling influences phase transitions in a two-component Bose gas in an optical lattice, revealing shifts in the Mott insulator to superfluid transition and mapping to an effective spin model.

## Contribution

It introduces a detailed analysis of the effects of coherent light-matter interactions on quantum phases using advanced theoretical methods.

## Key findings

- Coherent coupling shifts the Mott lobe tip to higher tunneling values.
- Strong inter-species repulsion affects the superfluid-Mott transition.
- The Bose-Hubbard model maps onto an effective spin Hamiltonian.

## Abstract

We investigate properties of an ultracold, two-component bosonic gas in a square optical lattice at unit filling. In addition to density-density interactions, the atoms are subject to coherent light-matter interactions that couple different internal states. We examine the influence of this coherent coupling on the system and its quantum phases by using Gutzwiller mean field theory as well as bosonic dynamical mean field theory. We find that the interplay of strong inter-species repulsion and coherent coupling affects the Mott insulator to superfluid transition and shifts the tip of the Mott lobe toward higher values of the tunneling amplitude. In the strongly interacting Mott regime, the resulting Bose-Hubbard model can be mapped onto an effective spin Hamiltonian that offers additional insights into the observed phenomena.