Valley Opto-Electronics in Dirac Materials
February 2nd, 2017 JUSTIN SONG California Institute of Technology

Dirac fermions possess emergent quantum mechanical behavior that can give rise to new, and unusual opto-electronic properties. One striking example is Berry curvature in "topologically"-flavored two-dimensional gapped Dirac materials (GDMs, e.g., TMDs, and gapped graphene heterostructures), or three dimensional Dirac and Weyl semimetals. In these, Berry curvature enable Hall currents in the absence of an applied magnetic field.

I will argue that Berry curvature can dramatically change the photoresponse of Dirac/Weyl materials, and may offer new opto-electronic functionality. One salient example is how photoresponse in GDMs with narrow bandgaps is enhanced by Berry curvature. In these materials, that include G/hBN, or dual-gated Bilayer graphene, even a small number of photoexcited carriers can carry large anomalous Hall currents - orders of magnitude larger than those previously observed in TMDs - enabling a new "Berry transport" regime to be accessed. Another example, are a new class of plasmons that exhibit chirality even in the absence of a magnetic field - chiral Berry plasmons (CBPs). CBPs are non-reciprocal, and may appear in a gamut of anomalous Hall metals that include photoexcited GDMs, metallic ferromagnets, as well as Weyl semimetals. CBP-based nonreciprocity, if realized experimentally, stands to play a vital role in the miniaturization of optical components that are magnetic field free.

Thursday, February 2, 2017, 12:00. Seminar Room

Hosted by Prof. Darrick Chang