The $\pi$ Berry Phase and Topological Excitation in Interacting Boson-Fermion Mixtures

TL;DR

This paper investigates the topological properties of a one-dimensional boson-fermion mixture in an optical superlattice, revealing a nontrivial Berry phase and gapless topological excitations relevant to cold atom experiments.

Contribution

It identifies a topological insulating phase in interacting boson-fermion mixtures characterized by a nontrivial Berry phase and analyzes the nature of topological excitations.

Findings

Topological insulating phase with nontrivial Berry phase identified

Boson-fermion exchanging excitation is gapless and topological

Results are experimentally relevant for cold atom systems

Abstract

The topological property of boson-fermion mixture in a one-dimensional optical superlattice is studied and the topological insulating phase of interacting boson-fermion mixture characterized by a nontrivial Berry phase is identified. The single-particle and boson-fermion exchanging excitation spectrums are calculated and we identify the boson-fermion exchanging excitation as the gapless topological excitation in the topological phase of the mixture. The different kinds of excitations are explained explicitly from the competition among the bulk gap, the on-site boson-boson and boson-fermion interactions. The Hamiltonian studied has been partly realized in the state-of-art cold atom experiments, and the results are very relevant to the experiments.