Title

Directly photoexcited Dirac and Weyl fermions in ZrSiS and NbAs

Document Type

Article

Publication Date

11-28-2018

Publisher

American Institute of Physics Publishing

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.

Comments

This is an author-created, un-copyedited version of an article accepted for publication in Applied Physics Letters.

Copyright © 2018 American Institute of Physics. Reprinted with permission.

Datasets are included as additional files.

supplementaryinformation.pdf (610 kB)
Supplementary Information

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