Continuous transition from Fermi liquid to A fractional Chern insulator

TL;DR

This paper develops a critical theory describing a continuous transition between a Fermi liquid and a fractional Chern insulator at filling 2/3, revealing new phases and transport behaviors relevant to moiré materials.

Contribution

It introduces a novel critical framework for the FL to FCI transition, including a transition from a composite Fermi liquid to a superfluid* phase with unique wavefunction and transport properties.

Findings

Fermi liquid near transition exhibits |z_i - z_j|^6 wavefunction factor

High-temperature transport resembles an anyon gas with /2 rac{h}{e^2} Hall resistivity

Low-temperature behavior recovers conventional Fermi liquid with zero Hall resistivity

Abstract

Recent experiments in moir\'e materials have observed fractional Chern insulators (FCI) at zero magnetic field, providing an opportunity to study the transition from FCI to the more conventional phases such as Fermi liquid (FL) and superconductor (SC) by tuning the interaction strength or bandwidth. In this work, we formulate a critical theory for a continuous transition at the filling $\nu=\frac{2}{3}$ between the FL and a FCI* phase that hosts an additional neutral sector, but has the same transport signatures as the usual FCI. In our framework, this corresponds to a transition from a composite Fermi liquid (CFL) to a superfluid* phase of the composite bosons. The Fermi liquid close to the transition has an additional factor $|z_i-z_j|^6$ in its wavefunction. Also, the transport behavior at high temperature on the FL side is actually like an `anyon gas' phase on top of the FCI, with $\rho_{xy}$ close to $\frac{3}{2}\frac{h}{e^2}$. FL behavior with $\rho_{xy} \approx 0$ is recovered only at very low temperature. We also briefly discuss the possibility of a chiral superconductor as the descendant of this strongly correlated FL and the potential relevance to the twisted MoTe$_2$ system.