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Beyond the lowest Landau level: Unlocking more robust fractional states using flat Chern bands with higher vortexability

Yitong Zhang1,*, Siddhartha Sarkar2,*, Xiaohan Wan1,3,*, Daniel E. Parker4,†, Shi-Zeng Lin5,6,‡, and Kai Sun1,§

  • *These authors contributed equally to this work.
  • †Contact author: danielericparker@ucsd.edu
  • ‡Contact author: szl@lanl.gov
  • §Contact author: sunkai@umich.edu
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Phys. Rev. B 114, 295111 – Published 12 November, 2026

DOI: https://doi.org/10.1103/5yrq-qjkh

Abstract

Enhancing the many-body gap of a fractional state is crucial for realizing robust fractional excitations. For fractional Chern insulators, existing studies suggest that making flat Chern bands closely resemble the lowest Landau level (LLL) seems to maximize the excitation gap, providing an apparently optimal platform. In this work, we demonstrate that deforming away from the LLL limit can, in fact, produce substantially larger fractional quantum Hall gaps. Using moiré flat bands with strongly non-Landau-level wave functions, we show that the gap can exceed that of the LLL by more than two orders of magnitude for short-range interactions and by factors of two to three for long-range interactions. This enhancement is generic across Abelian fractional Chern insulator states and follows a universal enhancement factor within each hierarchy. In the Landau-level framework, we identify the amplification of pseudopotentials as the microscopic origin of the observed enhancement. More generally, in a Chern band system where the pseudopotential decomposition is not well defined, we find a sharp scaling distinction: in the strongly screened regime, the ν=1/3 gap scales cubically with gate distance ds in the LLL and vortexable Chern bands, but linearly in higher-vortexable Chern bands. The activation of this leading O(ds) term by deviating from ideal quantum geometry is the key origin of the gap enhancement, and this criterion remains meaningful even without rotational symmetry. We further examined non-Abelian states and found that within finite-size resolution, this wave-function construction method can also be used to manipulate and enhance the gap for certain interaction parameters. We further discuss experimental implications of our findings in twisted bilayer MoTe2.

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Phys. Rev. B 114, 295111– Published 12 November, 2026
  • Received 20 November 2025
  • Revised 30 July 2026
  • Accepted 20 October 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by Max Planck Society.

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