Zero-field composite Fermi liquid in twisted semiconductor bilayers

TL;DR

This paper proposes a composite fermion framework to understand zero-field fractional quantum anomalous Hall states in twisted MoTe2, supported by exact diagonalization, and predicts experimental signatures like a Jain sequence and commensurability oscillations.

Contribution

It introduces the concept of anomalous composite Fermi liquids in twisted bilayers and develops a long-wavelength theory with testable experimental predictions.

Findings

Evidence for composite Fermi liquid states at zero magnetic field in tMoTe2.

Identification of anomalous composite Fermi liquids as central to the phase diagram.

Predictions of a Jain sequence of FQAH states and commensurability oscillations.

Abstract

Recent experiments have produced evidence for fractional quantum anomalous Hall (FQAH) states at zero magnetic field in the semiconductor moir\'e superlattice system $t$MoTe$_2$. Here we argue that a composite fermion description, already a unifying framework for the phenomenology of 2d electron gases at high magnetic fields, provides a similarly powerful perspective in this new context. To this end, we present exact diagonalization evidence for composite Fermi liquid states at zero magnetic field in $t$MoTe$_2$ at fillings $n=\frac{1}{2}$ and $n=\frac{3}{4}$. We dub these non-Fermi liquid metals anomalous composite Fermi liquids (ACFLs), and we argue that they play a central organizing role in the FQAH phase diagram. We proceed to develop a long wavelength theory for this ACFL state that offers concrete experimental predictions upon doping the composite Fermi sea, including a Jain sequence of FQAH states and a new type of commensurability oscillations originating from the superlattice potential intrinsic to the system.