Quantitative transport measurements of fractional quantum Hall energy gaps in edgeless graphene devices

TL;DR

This study demonstrates the fabrication of edgeless graphene devices revealing deep fractional quantum Hall states and explores the tunable nature of these states, including a valley-ordered state at a specific filling factor.

Contribution

It introduces dual graphite-gated edgeless graphene devices that enable detailed transport measurements of FQH energy gaps, revealing new phenomena and state transitions.

Findings

Deep FQH sequences observed in edgeless graphene devices

Tunable crossover between single- and multi-component FQH states

Discovery of an unexpected valley-ordered state at ν=-4

Abstract

Owing to their wide tunability, spin- and valley internal degrees of freedom, and low disorder, graphene heterostructures are emerging as a promising experimental platform for fractional quantum Hall (FQH) studies. Surprisingly, however, transport measurements reveal many fewer FQH states than bulk capacitive probes. Here, we report the fabrication of dual graphite-gated monolayer graphene devices in an edgeless Corbino-type geometry that showing deep FQH sequences. Thermal activation gaps reveal a tunable crossover between single- and multi-component FQH states in the zero energy Landau level, while the first Landau level is found to host an unexpected valley-ordered state at $\nu=-4$.