Physics (Internal)

Current at a distance and resonant transparency in Weyl semi-metals

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract Topology in various guises plays a central role in modern condensed matter physics. Although the original applications of topological ideas to band structures relied on the existence of a fully gapped bulk spectrum, more recently it has been recognized that protected surface states can arise even in gapless systems. The prototypical example of a gapless topological phase is a Weyl semi-metal. Surface Fermi arcs are the most prominent manifestation of the topological nature of Weyl semi- metals. In the presence of a static magnetic eld oriented perpendicular to the sample surface, their existence leads to unique inter-surface cyclotron orbits. We show how these inter-surface cyclotron orbits aect the electronic properties of Weyl semi-metals already at the semi-classical level. As a result, we are able to propose two experiments which directly probe the Fermi arcs: a magnetic eld dependent non-local DC voltage and sharp resonances in the transmission of electromagnetic waves at frequencies controlled by the eld. We show that these experiments do not rely on quantum me- chanical phase coherence, which renders them far more robust and experimentally accessible than quantum eects. We also comment on the applicability of these ideas to Dirac semimetals. [1] Y. Baum, E. Berg, S.A. Parameswaran and A. Stern, \Current at a distance and resonant transparency in Weyl semi-metals", cond-mat arXiv:1508.03047 (2015).