Quasi-one-dimensional Hall physics in the Harper-Hofstadter-Mott model

TL;DR

This paper explores the phase diagram of the Harper-Hofstadter-Mott model in a quasi-one-dimensional setting, revealing analogues of fractional quantum Hall phases and novel integer-filling behaviors using exact diagonalization and mean-field methods.

Contribution

It uncovers quasi-one-dimensional fractional quantum Hall phases and integer-filling gapped states in the Harper-Hofstadter-Mott model, highlighting effects of anisotropy and geometry.

Findings

Identification of fractional quantum Hall analogues at fillings 1/2 and 3/2

Observation of gapped integer-filling states with unique Hall responses

Use of exact diagonalization and mean-field approximation for analysis

Abstract

We study the ground-state phase diagram of the strongly interacting Harper-Hofstadter-Mott model at quarter flux on a quasi-one-dimensional lattice consisting of a single magnetic flux quantum in $y$-direction. In addition to superfluid phases with various density patterns, the ground-state phase diagram features quasi-one-dimensional analogues of fractional quantum Hall phases at fillings $\nu=1/2$ and $3/2$, where the latter is only found thanks to the hopping anisotropy and the quasi-one-dimensional geometry. At integer fillings - where in the full two-dimensional system the ground-state is expected to be gapless - we observe gapped non-degenerate ground-states: At $\nu=1$ it shows an odd 'fermionic' Hall conductance, while the Hall response at $\nu=2$ consists of the transverse transport of a single particle-hole pair, resulting in a net zero Hall conductance. The results are obtained by exact diagonalization and in the reciprocal mean-field approximation.