Fractional Quantum Hall States of Dipolar Gases in Chern Bands

TL;DR

This paper demonstrates the existence of fractional quantum Hall states in dipolar gases on Chern bands, showing their robustness and phase transitions under varying interaction strengths using exact diagonalization.

Contribution

It provides the first detailed analysis of FQH states in dipolar gases within Chern bands, including their stability and transition to other phases.

Findings

FQH states at specific fractional fillings are observed with a robust energy gap.

FQH states transition to normal or superfluid states as dipolar interactions decrease.

FQH states evolve into charge density wave states in the thin torus limit.

Abstract

We study fermions and hardcore bosons with long range dipolar interactions at fractional fillings in a topological checkerboard lattice with short-range hoppings up to next-next-nearest neighbors \cite{Neupert2011}. We consider the case that the dipoles are aligned in the perpendicular direction by an external field without the complication of anisotropic interaction. Using exact diagonalization, we find clear signatures of fractional quantum Hall (FQH) states at filling factors 1/3 and 1/5 for fermions (1/2 and 1/4 for bosons) in the lowest Chern band with a robust spectrum gap at moderate dipolar interaction strength. The robustness of these FQH states against long-range interaction tail and band flatness is investigated. When the dipolar interaction decreases, the fermionic FQH states turn into normal states, and the bosonic 1/4-FQH state turns into a superfluid state. The bosonic 1/2-FQH state survives even in the absence of the dipolar interaction, but vanishes when the hard core becomes a soft core with a critical onsite repulsion. In the thin torus limit, the static density structure factors indicates that the FQH state turns into a commensurate charge density wave (CDW) state.