Giant flavor-Hall effect in Dirac materials
Dimitry Abanin, Princeton University
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 stems from flavor splitting
induced by magnetic field, which leads to the imbalance of the Hall
resistivity for two flavor species. FHE 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.
[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.