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Helical quantum Hall phase in graphene on SrTiO3

Benjamin Sacépé - Néel Institute, CNRS Grenoble

Helical edge states in topological insulators have attracted a lot of attention due to the prospect of inducing and manipulating Majorana states in superconducting hybrid devices. Most topological insulators, however, are confronted with material issues such as bulk parasitic bulk conduction or inhomogeneous chemical potential. In this talk I will present a new type of topological insulator constructed on the basis of the quantum Hall effect of graphene. I will show that the ground state of charge neutral graphene under perpendicular magnetic field is a quantum Hall topological insulator with a ferromagnetic order that exhibits spin-filtered, helical edge channels. The topological phase emerges in the graphene zeroth Landau level via a suitable screening of the Coulomb interaction by a SrTiO3 high-k dielectric substrate. We observed robust helical edge transport emerging at a magnetic field as low as 1 T and withstanding temperatures up to 110 K over micron-long distances. I’ll also discuss recent scanning tunneling spectroscopy that evidences the (screened) interaction-induced ferromagnetic gap of the zeroth Landau level. This new topological graphene platform may open an alternative pathway for topological superconductivity.

L. Veyrat et al., Helical quantum Hall phase in graphene on SrTiO3, Science 367, 781 (2020)



  • Lundi 21 septembre 14:00-16:00 -

    Helical quantum Hall phase in graphene on SrTiO3

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