Weak topological insulating phases of hard-core-bosons on the honeycomb lattice

TL;DR

This paper identifies a weak topological insulator phase in hard-core bosons on a honeycomb lattice with alternating on-site potential, supported by quantum Monte Carlo simulations and analytical methods, and discusses its robustness and experimental feasibility.

Contribution

It introduces a weak topological insulator phase in a bosonic system on a honeycomb lattice with alternating potential, supported by numerical and analytical evidence.

Findings

Discovery of a weak topological insulator phase at specific fillings.

The phase is characterized by zero Chern number and non-zero Berry phase.

The phase remains stable against certain repulsive interactions.

Abstract

We study the phases of hard-core-bosons on a two-dimensional periodic honeycomb lattice in the presence of an on-site potential with alternating sign along the different y-layers of the lattice. Using quantum Monte Carlo simulations supported by analytical calculations, we identify a weak topological insulator, characterized by a zero Chern number but non-zero Berry phase, which is manifested at either density 1/4 or 3/4, as determined by the potential pattern. Additionally, a charge-density-wave insulator is observed at 1/2-filling, whereas the phase diagram at intermediate densities is occupied by a superfluid phase. The weak topological insulator is further shown to be robust against any amount of nearest-neighbor repulsion, as well as weak next-nearest-neighbor repulsion. The experimental realization of our model is feasible in an optical lattice setup.