Demixing Effects in Mixtures of Two Bosonic Species

TL;DR

This study uses quantum Monte Carlo simulations to explore the phase diagram of a two-boson species mixture in a lattice, revealing various demixed and mixed quantum phases depending on interaction strengths.

Contribution

It provides the first detailed phase diagram of two-component bosonic mixtures in a lattice, highlighting demixing phenomena and experimental detection methods.

Findings

Demixed superfluid and Mott-Insulator phases occur at high inter-species interactions.

Double-superfluid and supercounterflow phases are identified under different interaction regimes.

Demixing can be experimentally observed via anisotropic effects in time-of-flight images.

Abstract

Motivated by recent experiments on two-component systems, we investigate the ground-state phase diagram of a mixture of two bosonic species by means of path-integral quantum Monte Carlo by the two-worm algorithm. The mixture is trapped in a square lattice at half-filling conditions. Various quantum phases are stabilized depending on the interplay between intra- and inter-species interactions. We show that the phase diagram features a demixed superfluid phase and demixed Mott-Insulator phase when the inter-species interaction becomes greater than the intra-species repulsion, and a double-superfluid phase or a supercounterflow otherwise. We also show that demixing, characterized by spatial separation of the two species, can be detected experimentally through the effects of anisotropy revealed by time-of-flight images.