Quantum Hall Effect at 0.002T

TL;DR

This paper reports the observation of quantum Hall effects at extremely low magnetic fields in high-mobility double-layer graphene, facilitated by reduced sample inhomogeneity and enhanced carrier mobility.

Contribution

It introduces a double-layer graphene architecture with ultra-thin hBN that significantly reduces inhomogeneity, enabling the observation of quantum Hall phenomena at very low magnetic fields.

Findings

Quantum Hall effects observed below 1 mT

Integer quantum Hall at 0.002T

Fractional quantum Hall at 2T

Abstract

Graphene enables precise carrier-density control via gating, making it an ideal platform for studying electronic interactions. However, sample inhomogeneities often limit access to the low-density regimes where these interactions dominate. Enhancing carrier mobility is therefore crucial for exploring fundamental properties and developing device applications. Here, we demonstrate a significant reduction in external inhomogeneity using a double-layer graphene architecture separated by an ultra-thin hexagonal boron nitride layer. Mutual screening between the layers reduces scattering from random Coulomb potentials, resulting in a quantum mobility exceeding. Shubnikov de-Haas oscillations emerge at magnetic fields below 1 mT, while integer quantum Hall features are observed at 0.002T. Furthermore, we identify a fractional quantum Hall plateau at a filling factor of at 2T. These results demonstrate the platform's suitability for investigating strongly correlated electronic phases in graphene-based heterostructures.