Complex phases in the doped two-species bosonic Hubbard Model

TL;DR

This study uses Quantum Monte Carlo simulations to explore the rich phase diagram of a two-species bosonic Hubbard model, revealing five distinct phases including novel phase-separated states with mixed Mott and superfluid behaviors.

Contribution

It introduces a detailed phase diagram for a doped two-species bosonic Hubbard model, identifying new phase-separated states with unique properties.

Findings

Identified five distinct phases including a novel phase-separated region.

Discovered coexistence of anti-ferromagnetic and superfluid phases near half filling.

Revealed phase-separated Mott and superfluid behaviors at low temperatures.

Abstract

We study a two-dimensional bosonic Hubbard model with two hard-core species away from half filling using Quantum Monte Carlo simulations. The model includes a repulsive interspecies interaction and different nearest-neighbor hopping terms for the two species. By varying the filling we find a total of five distinct phases, including a normal liquid phase at higher temperature, and four different phases at lower temperature. We find an anti-ferromagnetically ordered Mott insulator and a region of coexistent anti-ferromagnetic and superfluid phases near half filling. Further away from half filling the phase diagram displays a superfluid phase and a novel phase inside the superfluid region at even lower temperatures. In this novel phase separated region, the heavy species has a Mott behavior with integer filling, while the lighter species shows phase separated Mott and superfluid behaviors.