Heteromoir\'e Engineering on Magnetic Bloch Transport in Twisted Graphene Superlattices

TL;DR

This paper investigates magnetic Bloch states in twisted graphene superlattices, revealing high-temperature oscillations linked to integer and fractional states, and explores how moiré superlattice structures influence electron transport.

Contribution

It reports the experimental observation of high-temperature Brown-Zak oscillations in twisted graphene, highlighting the role of moiré superlattices in magnetic Bloch transport.

Findings

Observation of high-temperature Brown-Zak oscillations in twisted graphene.

Coexistence of multiple periodic oscillations due to different moiré wavelengths.

Heteromoiré superlattices significantly influence magnetic Bloch transport.

Abstract

Localized electrons subject to applied magnetic fields can restart to propagate freely through the lattice in delocalized magnetic Bloch states (MBSs) when the lattice periodicity is commensurate with the magnetic length. Twisted graphene superlattices with moir\'e wavelength tunability enable experimental access to the unique delocalization in a controllable fashion. Here we report the observation and characterization of high-temperature Brown-Zak (BZ) oscillations which come in two types, 1/B and B periodicity, originating from the generation of integer and fractional MBSs, in the twisted bilayer and trilayer graphene superlattices, respectively. Coexisting periodic-in-1/B oscillations assigned to different moir\'e wavelengths, are dramatically observed in small-angle twisted bilayer graphene, which may arise from angle-disorder-induced in-plane heteromoir\'e superlattices. Moreover, the vertical stacking of heteromoir\'e supercells in double-twisted trilayer graphene results in a mega-sized superlattice. The exotic superlattice contributes to the periodic-in-B oscillation and dominates the magnetic Bloch transport.