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arXiv · 1907.02299

Helical quantum Hall phase in graphene on SrTiO$_3$

Louis Veyrat·Corentin Déprez·Alexis Coissard·Xiaoxi Li·Frédéric Gay·Kenji Watanabe·Takashi Taniguchi·Zheng Vitto Han·Benjamin A. Piot·Hermann Sellier·Benjamin Sacépé
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Abstract

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 SrTiO$_3$ 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.

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Louis Veyrat, Corentin Déprez, Alexis Coissard, Xiaoxi Li, Frédéric Gay, Kenji Watanabe, Takashi Taniguchi, Zheng Vitto Han, Benjamin A. Piot, Hermann Sellier, Benjamin Sacépé. 2019-07-04. Helical quantum Hall phase in graphene on SrTiO$_3$. https://doi.org/10.1126/science.aax8201

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