NEP Speaker, James Kolodzey, University of Delaware

Title: Weyltronics: An Introduction to Weyl Fermions for Optoelectronic Devices

Abstract

In 2015, an interesting low energy excitation in condensed matter that mimics the massless, spin-polarized transport of Weyl fermions was experimentally discovered by three independent research groups.  Two of these discoveries were in inversion-breaking zero-bandgap semimetals, and one in inversion-breaking photonic crystals.  Although predicted in 1929, Weyl fermions remained an elusive theoretical possibility, until now.  Recent experiments showed that Weyl fermions have linear (rather than parabolic) dispersion bands and topological (i.e. insensitivity to smooth deformations) invariant properties that enable a variety of novel phenomena including surface Fermi arcs, the chiral anomaly, negative magnetoresistance, nonlocal transport, and photogalvanic currents. 

Weyl fermions may have a significant impact on the future of optoelectronics.  Their transport is spin-locked for reduced scattering and exceptionally high carrier mobilities and velocities, which may enable very fast devices and circuits.  Optical absorption in the far-infrared is circular polarization dependent.  Importantly, the current flow may be nearly dissipationless for ultra low-power operation, which is a crucial requirement for integrated circuits. 

As the first in a two-part series, this talk will be a tutorial introducing Weyl fermions and reviewing recent developments.  The topics will lead up to, and conclude with, a brief discussion of candidates for exotic optoelectronic devices.  Further details about the characteristics and limitations of anticipated Weyl fermion devices and the status of Weyl research at the University of Delaware will be presented as a second talk in the near future.

Bio

Dr. James Kolodzey is the Charles Black Evans Professor, Emeritus, in the NEP Group of the Department of Electrical and Computer Engineering, University of Delaware.