Exotic Haldane Superfluid Phase of Soft-Core Bosons in Optical Lattices

TL;DR

This paper proposes and confirms through quantum Monte Carlo simulations the existence of an exotic Haldane superfluid phase in a two-leg ladder Bose-Hubbard model, combining superfluidity with topological order.

Contribution

It introduces the Haldane superfluid phase in a bosonic system and demonstrates its properties using large-scale simulations, expanding understanding of topological phases in cold atom systems.

Findings

Identification of the Haldane superfluid phase in the model

Demonstration of coexistence of superfluidity and topological order

Analysis of effects of varying the number of ladder legs

Abstract

We propose to realize an exotic Haldane superfluid (HSF) phase in an extended Bose-Hubbard model on the two-leg ladder (i.e., a two-species mixture of interacting bosons). The proposal is confirmed by means of large-scale quantum Monte Carlo simulations, with a significant part of the ground-state phase diagram being revealed. Most remarkably, the newly discovered HSF phase features both superfluidity and the non-local topological Haldane order. The effects induced by varying the number of legs are furthermore explored. Our results shed light on how topological superfluid emerges in bosonic systems.