High quality magnetotransport in graphene using the edge-free Corbino geometry

TL;DR

This paper demonstrates high-quality magnetotransport measurements in graphene using a Corbino geometry, achieving improved quantum Hall effect resolution and revealing phase transitions and electron solid phases.

Contribution

It introduces a Corbino device design for graphene that eliminates edge effects, enabling clearer observation of quantum Hall states and phase transitions.

Findings

Enhanced resolution of integer and fractional quantum Hall states.

Identification of phase transitions in fractional Landau levels.

Observation of features consistent with electron solid phases.

Abstract

We report fabrication of graphene devices in a Corbino geometry consisting of concentric circular electrodes with no physical edge connecting the inner and outer electrodes. High device mobility is realized using boron nitride encapsulation together with a dual-graphite gate structure. Bulk conductance measurement in the quantum Hall effect (QHE) regime outperforms previously reported Hall bar measurements, with improved resolution observed for both the integer and fractional QHE states. We identify apparent phase transitions in the fractional sequence in both the lowest and first excited Landau levels (LLs) and observed features consistent with electron solid phases in higher LLs.