Chiral Second-Sound Collective Modes at the Edge of 2D Systems with a Nontrivial Berry Curvature.
We study the thermal transport in two-dimensional systems with a nontrivial Berry curvature texture. The physical realizations are many; for the sake of definiteness, we consider undoped graphene gapped by the presence of an aligned hexagonal-boron-nitride substrate. The same phenomenology applies, i.e., to surface states of 3D topological insulators in the presence of a uniform magnetization. We find that chiral valley-polarized second-sound collective modes propagate along the edges of the system. The localization length of the edge modes has a topological origin stemming from the anomalous velocity term in the quasiparticle current. At low temperature, the single-particle contribution to the transverse thermal conductance is exponentially suppressed, and only second-sound modes carry heat along the boundary. A sharp change in the behavior of the thermal Hall conductance, extracted from nonlocal measurements of the temperature along the edge, marks the onset of ballistic heat transport due to second-sound edge modes.
Radboud University, Institute for Molecules and Materials, NL-6525 AJ Nijmegen, The Netherlands.
Alessandro
A
Principi
Radboud University, Institute for Molecules and Materials, NL-6525 AJ Nijmegen, The Netherlands.
Mikhail I
MI
Katsnelson
Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Alex
A
Levchenko