Disorder-enhanced quantum transport in twisted bilayer graphene near the magic angle
Phys. Rev. B 113, 155421 – Published 13 April, 2026
DOI: https://doi.org/10.1103/9lc1-9m8t
Abstract
In disordered lattices, itinerant electrons typically undergo Anderson localization due to random phase interference, which suppresses their motion. By contrast, in flat-band systems where electrons are intrinsically localized owing to their vanishing group velocity, the role of disorder remains elusive. Twisted bilayer graphene (TBG) at the magic angle provides a representative flat-band platform to investigate this problem. Here, we perform an atomistic tight-binding quantum transport calculation on the interplay between disorder and flat bands in TBG devices. This nonphenomenological approach confirms that moderate disorder enhances conductance, whereas stronger disorder restores localization, revealing a disorder-driven delocalization-to-localization transport behavior. The underlying physical mechanism is understood by an effective intermoiré tunneling strength via spectral flow analysis of a disordered TBG cylinder. Moreover, by comparing magic-angle and large-angle TBG, we demonstrate qualitatively distinct disorder responses tied to the presence of flat bands. Our quantitative results highlight the unconventional role of disorder in flat-band moiré materials and offer insights into the observation of the fractional quantum anomalous Hall effect in disordered moiré systems.
