Directly photoexcited Dirac and Weyl fermions in ZrSiS and NbAs
Abstract
We report ultrafast optical measurements of the Dirac line-node semimetal ZrSiS and the Weyl semimetal NbAs, using mid-infrared pump photons from 86 meV to 500 meV to directly excite Dirac and Weyl fermions within the linearly dispersing bands. In NbAs, the photoexcited Weyl fermions initially form a non-thermal distribution, signified by a brief spike in the differential reflectivity whose sign is controlled by the relative energy of the pump and probe photons. In ZrSiS, electron-electron scattering rapidly thermalizes the electrons, and the spike is not observed. Subsequently, hot carriers in both materials cool within a few picoseconds. This cooling, as seen in the two materials' differential reflectivity, differs in sign, shape, and timescale. Nonetheless, we find that it may be described in a simple model of thermal electrons, without free parameters. The electronic cooling in ZrSiS is particularly fast, which may make the material useful for optoelectronic applications.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 26, 2018
- Source ID
- 10.1063/1.5055207
Entities
People
- Alex Nateprov
- Bala Murali Krishna Mariserla
- Bettina Lotsch
- C. Weber
- Ernest Arushanov
- Hans A. Bechtel
- J. Matthew Kim
- Keshav M Dani
- Leslie M Schoop
- Mazhar Ali
- Robert C. Newby
- Stuart Parkin
Organizations
- Army Research Office
- Central University of Karnataka
- Institute of Applied Physics
- Lawrence Berkeley National Laboratory
- Ludwig-Maximilians-Universität München
- Max Planck Institute for Microstructure Physics
- Max Planck Institute for Solid State Research
- National Science Foundation
- Okinawa Institute of Science and Technology
- Princeton University
- Santa Clara University
- United States Department of Energy