Snake Trajectories in Ultraclean Graphene p-n Junctions

TL;DR

This paper reports the observation of snake states in ultraclean graphene p-n junctions, showing magneto-conductance oscillations at low magnetic fields, supported by quantum simulations and enabled by Klein collimation.

Contribution

It demonstrates the first clear experimental observation of snake states in ballistic graphene p-n junctions with high visibility and tunability, supported by quantum transport simulations.

Findings

Magneto-conductance oscillations due to snake states observed at 20mT.

Visibility of oscillations reaches 30% thanks to Klein collimation.

Device operates effectively across different magnetic field regimes.

Abstract

Snake states are trajectories of charge carriers curving back and forth along an interface. There are two types of snake states, formed by either inverting the magnetic field direction or the charge carrier type at an interface. Whereas the former has been demonstrated in GaAs-AlGaAs heterostructures, the latter has become conceivable only with the advance of ballistic graphene where a gapless p-n interface governed by Klein tunneling can be formed. Such snake states were hidden in previous experiments due to limited sample quality. Here we report on magneto-conductance oscillations due to snake states in a ballistic suspended graphene p-n-junction which occur already at a very small magnetic field of 20mT. The visibility of 30% is enabled by Klein collimation. Our finding is firmly supported by quantum transport simulations. We demonstrate the high tunability of the device and operate it in different magnetic field regimes