Dirac materials, such as graphene and topological insulators, are a new class of two-dimensional materials where carriers have quasi-relativistic dispersion. While many new charge-related phenomena in Dirac materials have been discovered in the recent years, accessing neutral degrees of freedom (e.g., spin and valley in graphene) proved very challenging. In this work, I will propose a method to generate/detect neutral degrees of freedom in Dirac materials. I will also describe its experimental realization in graphene. I will show that flavor and charge currents are intertwined via flavor-Hall effect (FHE) when Dirac fermions are subject to weak magnetic field. The effect is giant near the Dirac point, where it can exceed the conventional spin-orbit-based spin-Hall effect by three orders of magnitude. In the experiment, FHE manifests itself in nonlocal all-electric transport: electric current generates flavor current, which propagates far away from source and drain, where it converts to a measurable charge voltage. The experimental observation of nonlocal transport in graphene is in agreement with the theoretical predictions. This work opens up new opportunities for manipulating neutral degrees of freedom in Dirac materials.
Reference: [1] D. A. Abanin, S. V. Morozov, L. A. Ponomarenko, R. V. Gorbachev, A. S. Mayorov, M. I. Katsnelson, K. S. Novoselov, L. S. Levitov, A. K. Geim, Nonlocal Transport and the Flavor Hall Effect at the Neutrality Point in Graphene , submitted.