Microscopic Mechanism of Anyon Superconductivity Emerging from Fractional Chern Insulators

TL;DR

This paper proposes a microscopic mechanism for anyon-induced superconductivity emerging from fractional Chern insulators, highlighting the role of quantum phase transitions into semion crystal states and their potential realization in moiré materials.

Contribution

It demonstrates how a natural energy hierarchy of anyons arises in FCIs near a quantum phase transition, providing a microscopic basis for anyon superconductivity with repulsive interactions.

Findings

Tensor network simulations show transition from FCI to semion crystal.

Enhanced Cooper pairing near the transition supports charge-2e superconductivity.

Doping near the transition leads to stable anyon pairing and chiral edge modes.

Abstract

Fractional quantum Hall (FQH) states and superconductors typically require contrasting conditions, yet recent experiments have observed them in the same device. A natural explanation is that mobile anyons give rise to superconductivity; however, this mechanism requires binding of minimally charged anyons to establish an unusual energy hierarchy. This scenario has mostly been studied with effective theories, leaving open the question of how anyon superconductivity can arise from repulsive interactions. Here, we show that such an energy hierarchy of anyons arises naturally in fractional Chern insulators (FCIs) at fillings $\nu = 2/(4p \mp 1)$ when they are driven toward a quantum phase transition into a ``semion crystal'' -- an exotic charge-density-wave (CDW) insulator with semion topological order. Near the transition, Cooper-pair correlations are enhanced, so that a conventional charge-2e superconductor appears with doping. Guided by these insights, we analyze a microscopic realization in a repulsive Hubbard-Hofstadter model. Tensor network simulations at $\nu = 2/3$ reveal a robust FCI that, with increasing interactions, transitions into the semion crystal. Finding a stable semion crystal in such a minimal model highlights it as a viable state competing with conventional CDW and FQH states. In the vicinity of this transition, we find markedly enhanced Cooper pairing, consistent with our theory that the 2e/3 anyon is cheaper than a pair of isolated e/3 anyons. Doping near the transition should in general lead to doping Cooper pairs and charge-2e superconductivity, with chiral edge modes of alternating central charge $c = \pm2$, which can coexist with translation symmetry breaking. Our framework unifies recent approaches to anyon superconductivity, reconciles it with strong repulsion and provides guidance for flat band moir\'e materials such as recent experiments in twisted MoTe$_2$.