Quantum Hall effect at 0.002 T in graphene.

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 <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>1</mn> <msup><mrow><mn>0</mn></mrow> <mrow><mn>7</mn></mrow> </msup> <mi>c</mi> <msup><mrow><mi>m</mi></mrow> <mrow><mn>2</mn></mrow> </msup> <msup><mrow><mi>V</mi></mrow> <mrow><mo>-</mo> <mn>1</mn></mrow> </msup> <msup><mrow><mi>s</mi></mrow> <mrow><mo>-</mo> <mn>1</mn></mrow> </msup> </math> . Shubnikov-de Haas oscillations emerge at magnetic fields below 1 mT, while integer quantum Hall features are observed at 0.002 T. Furthermore, we identify a fractional quantum Hall plateau at a filling factor of <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>v</mi></mrow> <mrow><mi>tot</mi></mrow> </msub> <mo>=</mo> <mo>-</mo> <mn>10</mn> <mo>/</mo> <mn>3</mn></math> at 2 T. These results demonstrate the platform's suitability for investigating strongly correlated electronic phases in graphene-based heterostructures.