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Résumé |
Helical edge states in topological insulators and semiconducting nanowires are attracting a tremendous
amount of attention due to the prospect of inducing and manipulating Majorana states in superconducting
hybrid devices. However, most of the topological systems studied so far for Majorana physics remain
obscured by 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. This new and versatile graphene platform opens up a promising avenue for topological
superconductivity. |
