Measurable signatures of bosonic fractional Chern insulator states and their fractional excitations in a quantum-gas microscope

TL;DR

This paper demonstrates that small, realistic quantum-gas microscope systems can host fractional Chern insulator states with clear signatures of fractional excitations, making experimental observation feasible.

Contribution

It shows that fractional Chern insulator states and their fractional excitations can be stabilized and detected in small, finite bosonic systems with realistic experimental setups.

Findings

Incompressible bulk density at expected filling in small systems

Clear signatures of fractional charge excitations

Robustness of signatures against particle number variations

Abstract

The recent progress in engineering topological band structures in optical-lattice systems makes it promising to study fractional Chern insulator states in these systems. Here we consider a realistic finite system of a few repulsively interacting bosons on a square lattice with magnetic flux and sharp edges, as it can be realized in quantum-gas microscopes. We investigate under which conditions a fractional Chern insulator state corresponding to the Laughlin-like state at filling $\nu=1/2$ can be stabilized and its fractional excitations probed. Using numerical simulations, we find an incompressible bulk density at the expected filling for systems, whose linear extent is as small as 6-8 sites. This is a promising result, since such small systems are favorable with respect to the required adiabatic state preparation. Moreover, we also see very clear signatures of excitations with fractional charge in response both to static pinning potentials and dynamical flux insertion. Since the compressible edges, which are found to feature chiral currents, can serve as a reservoir, these observations are robust against changes in the total particle number. Our results suggest that signatures of both a fractional Chern insulator state and its fractional excitations can be found under realistic experimental conditions.