Spinless and spinful charge excitations in moir\'e Fractional Chern Insulators

TL;DR

This study investigates spin-dependent charge excitations in moiré Fractional Chern Insulators, revealing that spin-preserving excitations have smaller gaps and exhibit dispersive behavior, advancing understanding of their fundamental properties.

Contribution

The paper introduces a method to analyze spinful and spinless excitations in FCIs, highlighting their energetic differences and dispersive nature, supported by large-scale exact diagonalization calculations.

Findings

Spin-preserving excitations have smaller energy gaps than spin-flipping ones.

Excitations show significant dispersion and emergent magnetic translation symmetry.

Results align qualitatively with experimental magnetic field dependence of transport gaps.

Abstract

Fractionally charged elementary excitations, the quasi-electron and quasi-hole, are one of the hallmarks of the fractional Chern insulator (FCI). In this work, we observe that spontaneous spin polarization in twisted MoTe$_2$ leads to multiple species of low-energy quasi-particles distinguished by their spin quantum numbers. We perform large-scale exact diagonalization (ED) calculations to investigate the nature of these excitations and develop a method to extract their fundamental energetic properties. Focusing on $\theta = 3.7^{\circ}$ and filling factor $\nu = -2/3$ relevant to recent experiments, we show that spin-preserving (spinless) charge excitations have smaller gap than spin-flipping (spinful) excitations both with and without band mixing. This result is in qualitative agreement with the measured magnetic field dependence of the transport gaps. Beyond the spinless and spinful quasi-particle gaps, we extract the full quasi-electron and quasi-hole ``band structure'' and find significant dispersion with emergent magnetic translation symmetry -- a fundamental departure from the immobile excitations of the quantum Hall fluid. Our results establish a framework for computing the properties of novel elementary excitations in FCIs.