High-temperature quantum oscillations caused by recurring Bloch states in graphene superlattices

TL;DR

This paper reports a new type of quantum oscillations in graphene superlattices that persist at high temperatures without Landau quantization, due to recurring changes in electronic structure related to Hofstadter butterfly physics.

Contribution

It introduces a novel high-temperature quantum oscillation phenomenon in graphene superlattices independent of Landau levels, expanding understanding of quantum effects in such systems.

Findings

Quantum oscillations persist above room temperature.

Oscillations are caused by effective zero magnetic field at certain flux fractions.

Phenomenon linked to Hofstadter butterfly physics.

Abstract

Cyclotron motion of charge carriers in metals and semiconductors leads to Landau quantization and magneto-oscillatory behavior in their properties. Cryogenic temperatures are usually required to observe these oscillations. We show that graphene superlattices support a different type of quantum oscillations that do not rely on Landau quantization. The oscillations are extremely robust and persist well above room temperature in magnetic fields of only a few T. We attribute this phenomenon to repetitive changes in the electronic structure of superlattices such that charge carriers experience effectively no magnetic field at simple fractions of the flux quantum per superlattice unit cell. Our work points at unexplored physics in Hofstadter butterfly systems at high temperatures.