Breakdown of zero-energy quantum Hall state in graphene in the light of current fluctuations and shot noise

TL;DR

This paper explores the transition from Zener tunneling to avalanche electron transport in suspended graphene under high magnetic fields, revealing electron bunching, noise characteristics, and correlations in the quantum Hall regime.

Contribution

It provides new insights into the crossover from single-electron tunneling to avalanche transport in graphene, with detailed noise and correlation analysis.

Findings

Zener tunneling behavior observed at low bias

Avalanche transport emerges at higher bias and magnetic fields

Strong electron bunching and correlations within avalanches

Abstract

We have investigated the cross-over from Zener tunneling of single charge carriers to avalanche type of bunched electron transport in a suspended graphene Corbino disk in the zeroth Landau level. At low bias, we find a tunneling current that follows the gyrotropic Zener tunneling behavior. At larger bias, we find avalanche type of transport that sets in at a smaller current the larger the magnetic field is. The low-frequency noise indicates strong bunching of the electrons in the avalanches. On the basis of the measured low-frequency switching noise power, we deduce the characteristic switching rates of the avalanche sequence. The simultaneous microwave shot noise measurement also reveals intrinsic correlations within the avalanche pulses and indicate decrease of correlations with increasing bias.