Large tunable valley splitting in edge-free graphene quantum dots on boron nitride

Category: Scientific Highlights

Published in Nature Nanotechnology

Coherent manipulation of the binary degrees of freedom is at the heart of modern quantum technologies. Graphene offers two binary degrees: the electron spin and the valley. Efficient spin control has been demonstrated in many solid-state systems, whereas exploitation of the valley has only recently been started, albeit without control at the single-electron level. Here, we show that van der Waals stacking of graphene onto hexagonal boron nitride offers a natural platform for valley control. We use a graphene quantum dot induced by the tip of a scanning tunnelling microscope and demonstrate valley splitting that is tunable from −5 to +10 meV (including valley inversion) by sub-10-nm displacements of the quantum dot position. This boosts the range of controlled valley splitting by about one order of magnitude. The tunable inversion of spin and valley states should enable coherent superposition of these degrees of freedom as a first step towards graphene-based qubits.

Project Part: P05 Embedded cluster approach and non-adiabatic processes in physics and chemistry

Original Publication: Nils M. Freitag, Tobias Reisch, Larisa A. Chizhova, Péter Nemes-Incze, Christian Holl, Colin R. Woods, Roman V. Gorbachev, Yang Cao, Andre K. Geim, Kostya S. Novoselov, Joachim Burgdörfer, Florian Libisch, Markus Morgenstern

DOI 10.1038/s41565-018-0080-8

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