Anyon superconductivity and plateau transitions in doped fractional quantum anomalous Hall insulators

TL;DR

This paper explains recent experimental evidence of superconductivity and RIQAH phases in doped fractional quantum anomalous Hall insulators through disorder effects on composite fermions, linking plateau transitions to these phases.

Contribution

It introduces a model where doping anyons causes plateau transitions of composite fermions into quantum Hall states, explaining superconductivity and RIQAH phases.

Findings

Quantitative predictions match experimental critical behavior.

Superfluid stiffness relates to CF polarizability.

Disorder effects on CF Landau-Hofstadter bands explain observations.

Abstract

Recent experiments reported evidence of superconductivity and re-entrant integer quantum anomalous Hall (RIQAH) insulator upon doping the $\nu_e = 2/3$ fractional quantum anomalous Hall states (FQAH) in twisted MoTe${}_2$, separated by narrow resistive regions. Anyons of a FQAH generally have a finite effective mass, and when described by anyon-flux composite fermions (CF), experience statistical magnetic fields with a commensurate filling. Here, we show that most of the experimental observations can be explained by invoking the effects of disorder on the Landau-Hofstadter bands of CFs. In particular, by making minimal assumptions about the anyon energetics and dispersion, we show that doping anyons drives plateau transitions of CFs into integer quantum Hall states, which physically corresponds to either to a superconductor or to a RIQAH phase. We develop a dictionary that allows us to infer the response in these phases and the critical regions from the knowledge of the response functions of the plateau transitions. In particular, this allows us to relate the superfluid stiffness of the superconductor to the polarizability of CFs. As a first step towards a quantitative understanding, we borrow results from the celebrated integer quantum Hall plateau transitions to make quantitative prediction for the critical behavior of the superfluid stiffness, longitudinal and Hall conductivity, and response to out-of-plane magnetic field, all of which agree reasonably well with the experimental observations. Our results provide strong support for anyon superconductivity being the mechanism for the observed superconductor in the vicinity of the $\nu_e = 2/3$ FQAH insulator.