Mott Insulator to Superfluid transition in Bose-Bose mixtures in a two-dimensional lattice

TL;DR

This study uses Monte Carlo simulations to analyze how a second bosonic species influences the Mott insulator to superfluid transition in a two-dimensional lattice, revealing boundary modifications and polaron-like excitations.

Contribution

It provides the first detailed numerical analysis of two-component bosonic mixtures in 2D lattices, highlighting boundary shifts and excitations due to interspecies interactions.

Findings

Lower Mott lobe boundary is strongly renormalized at low second component filling.

Upper boundary is affected only at high second component filling.

Evidence of polaron-like excitations in the system.

Abstract

We perform a numeric study (Worm algorithm Monte Carlo simulations) of ultracold two-component bosons in two-dimensional optical lattices. We study how the Mott insulator to superfluid transition is affected by the presence of a second superfluid bosonic species. We find that, at fixed interspecies interaction, the upper and lower boundaries of the Mott lobe are differently modified. The lower boundary is strongly renormalized even for relatively low filling factor of the second component and moderate (interspecies) interaction. The upper boundary, instead, is affected only for large enough filling of the second component. Whereas boundaries are renormalized we find evidence of polaron-like excitations. Our results are of interest for current experimental setups.