Resonant tunnelling between the chiral Landau states of twisted graphene lattices

TL;DR

This paper investigates resonant tunnelling between chiral Landau states in twisted graphene layers, revealing conservation of energy, momentum, and chirality, and demonstrating Klein tunnelling phenomena in multilayered van der Waals heterostructures.

Contribution

It provides experimental evidence of inter-Landau level tunnelling conserving key electron properties and introduces Klein tunnelling as a mechanism in twisted graphene multilayers.

Findings

Resonant tunnelling preserves electron energy, momentum, and chirality.

Inter-Landau level transitions are demonstrated under magnetic fields.

Klein tunnelling is observed in inter-layer transitions.

Abstract

A new class of multilayered functional materials has recently emerged in which the component atomic layers are held together by weak van der Waals forces that preserve the structural integrity and physical properties of each layer. An exemplar of such a structure is a transistor device in which relativistic Dirac Fermions can resonantly tunnel through a boron nitride barrier, a few atomic layers thick, sandwiched between two graphene electrodes. An applied magnetic field quantises graphene's gapless conduction and valence band states into discrete Landau levels, allowing us to resolve individual inter-Landau level transitions and thereby demonstrate that the energy, momentum and chiral properties of the electrons are conserved in the tunnelling process. We also demonstrate that the change in the semiclassical cyclotron trajectories, following a tunnelling event, is a form of Klein tunnelling for inter-layer transitions.