Complete phase diagram and topological properties of interacting bosons in one-dimensional superlattices

TL;DR

This paper maps out the complete phase diagram of interacting bosons in 1D superlattices, revealing topological insulators characterized by Berry phase and boundary states, using atomic-limit analysis and quantum Monte Carlo simulations.

Contribution

It provides the first comprehensive phase diagram including topological properties of interacting bosons in 1D superlattices, identifying emergent topological insulators.

Findings

All emergent insulators are topological with Berry phase π.

Identified three phases: superfluid, charge-density-wave, Mott insulators.

Higher filling topological phases relate to 1/3-filling topological states.

Abstract

The interacting bosons in one-dimensional inversion-symmetric superlattices are investigated from the topological aspect. The complete phase diagram is obtained by an atomic-limit analysis and quantum Monte Carlo simulations and comprises three kinds of phases: superfluid, persisted charge-density-wave and Mott insulators, and emergent insulators in the presence of nearest-neighbor hoppings. We find that all emergent insulators are topological, which are characterized by the Berry phase $\pi$ and a pair of degenerate in-gap boundary states. The mechanism of the topological bosonic insulators is qualitatively discussed and the ones with higher fillings can be understood as a $\frac{1}{3}$-filling topological phase on a background of trivial charge-density-wave or Mott insulators.