Proximity screening greatly enhances electronic quality of graphene

Abstract

Abstract The electronic quality of two-dimensional systems is crucial when exploring quantum transport phenomena. In semiconductor heterostructures, decades of optimization have yielded record-quality two-dimensional gases with transport and quantum mobilities reaching close to 10 8 and 10 6 cm 2 V −1 s −1 , respectively 1–10 . Although the quality of graphene devices has also been improving, it remains comparatively lower 11–17 . Here we report a transformative improvement in the electronic quality of graphene by employing graphite gates placed in its immediate proximity, at 1 nm separation. The resulting screening reduces charge inhomogeneity by two orders of magnitude, bringing it down to a few 10 7 cm −2 and limiting potential fluctuations to less than 1 meV. Quantum mobilities reach 10 7 cm 2 V −1 s −1 , surpassing those in the highest-quality semiconductor heterostructures by an order of magnitude, and the transport mobilities match their record 9,10 . This quality enables Shubnikov–de Haas oscillations in fields as low as 1 mT and quantum Hall plateaux below 5 mT. Although proximity screening predictably suppresses electron–electron interactions, fractional quantum Hall states remain observable with their energy gaps reduced only by a factor of 3–5 compared with unscreened devices, demonstrating that many-body phenomena at spatial scales shorter than 10 nm remain robust. Our results offer a reliable route to improving electronic quality in graphene and other two-dimensional systems, which should facilitate the exploration of new physics previously obscured by disorder.