Non-linear Landau fan diagram for graphene electrons exposed to a moir\'e potential

TL;DR

This paper investigates unusual conductance oscillations in graphene under a moiré potential, revealing non-linear Landau fan diagrams caused by multiple miniband occupation and magnetic breakdown, challenging the typical flux-linear behavior.

Contribution

It demonstrates that graphene electrons in a moiré potential exhibit non-linear Landau fan diagrams due to complex miniband interactions and magnetic breakdown effects.

Findings

Observed non-linear Landau fan diagrams in graphene with moiré potential

Attributed anomalies to multiple miniband occupation and magnetic breakdown

Challenged the conventional flux-linear Landau fan behavior

Abstract

Due to Landau quantization, the conductance of two-dimensional electrons exposed to a perpendicular magnetic field exhibits oscillations that generate a fan of linear trajectories when plotted in the parameter space spanned by density and magnetic field. This fan looks identical irrespective of the electron dispersion details that determines the field dependence of the Landau level energy. This is no surprise, since the position of conductance minima solely depends on the level degeneracy which is linear in flux. The fractal energy spectrum that emerges within each Landau band when electrons are also exposed to a two-dimensional superlattice potential produces numerous additional oscillations, but they too create just linear fans for the same reason. Here, we report on conductance oscillations of graphene electrons exposed to a moir\'e potential that defy this general rule of flux linearity and attribute the anomalous behavior to the simultaneous occupation of multiple minibands and magnetic breakdown.