Crystal, Superfluids, Supersolid and Hetero-Structure in System of Two-Component Strongly-Correlated Bosons in a Cubic Optical Lattice

TL;DR

This paper investigates the finite-temperature phase diagram of two-component strongly-correlated bosons in a cubic optical lattice, revealing various phases including superfluid, insulator, phase separation, and supersolid, with implications for high-temperature superconductivity.

Contribution

It introduces the bosonic t-J model for two-component bosons and demonstrates how inter-species attraction induces a supersolid phase with paired superfluidity.

Findings

Rich phase structure including superfluid, insulator, and phase-separated states

Supersolid phase emerges due to nearest-neighbor inter-species attraction

Paired superfluid coexists with single-atom superfluid in the supersolid state

Abstract

In the present paper, we study finite-temperature phase structure of two-component hard-core bosons in a cubic optical lattice. The system that we study in the present paper is an effective model for the Bose-Hubbard model with strong on-site repulsions and is called bosonic t-J model. This model is a bosonic counterpart of the t-J model for the strongly-correlated electron systems like the high-temperature superconducting materials. We study the model by means of path-integral methods and Monte-Carlo simulations. We found that this system has a very rich phase structure including checkerboard-type "insulating" state, superfluid, phase-separated state, inhomogeneous cloudlet state, etc. We are also interested in the possible supersolid phase with both the checkerboard order and superfluidity and found that additional nearest-neighbor inter-species attractive force induces the supersolid state. In the supersolid state, paired superfluid appears in addition to the superfluid of single atom. This result gives important insight into mechanism of the high-temperature superconductivity of the cuprate.