The ground state of charge neutral graphene under perpendicular magnetic field was predicted to be a quantum Hall topological insulator with a ferromagnetic order and spin-filtered, helical edge channels. In most experiments, however, an otherwise insulating state is observed and is accounted for by lattice-scale interactions that promote a broken-symmetry state with gapped bulk and edge excitations. We tuned the ground state of the graphene zeroth Landau level to the topological phase via a suitable screening of the Coulomb interaction with a SrTiO3 high-k dielectric substrate. We observed robust helical edge transport emerging at a magnetic field as low as 1 tesla and withstanding temperatures up to 110 kelvins over micron-long distances. This new and versatile graphene platform opens new avenues for spintronics and topological quantum computation.
@article{arxiv.1907.02299,
title = {Helical quantum Hall phase in graphene on SrTiO$_3$},
author = {Louis Veyrat and Corentin Déprez and Alexis Coissard and Xiaoxi Li and Frédéric Gay and Kenji Watanabe and Takashi Taniguchi and Zheng Vitto Han and Benjamin A. Piot and Hermann Sellier and Benjamin Sacépé},
journal= {arXiv preprint arXiv:1907.02299},
year = {2020}
}