Directly photoexcited Dirac and Weyl fermions in ZrSiS and NbAs

ORAL

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.

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Presenters

  • Jaehun Kim

    • Santa Clara University

Authors

  • Jaehun Kim

    • Santa Clara University

  • Christopher P Weber

    • Santa Clara University

  • Leslie Schoop

    • Princeton University
    • Chemistry, Princeton University
    • Department of Chemistry, Princeton University
    • Chemistry, Princeton

  • Stuart S P Parkin

    • Max Plank Institute for Microstructure Physics
    • Max-Planck Institute of Microstructure Physics
    • Max Planck Institute of Microstructure Physics

  • Robert Newby

    • Santa Clara University

  • Alexandr Nateprov

    • Applied Physics, Academy of Sciences of Moldova

  • Bettina Lotsch

    • Max Planck Institute for Solid State Research
    • Nanochemistry department, Max-Planck-Institute for Solid State Research

  • M. Bala Murali Krishna

    • Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University

  • Keshav M Dani

    • Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University

  • Hans Bechtel

    • Advanced Light Source Division, Lawrence Berkeley National Laboratory
    • Lawrence Berkeley National Laboratory

  • Ernest Arushanov

    • Applied Physics, Academy of Sciences of Moldova

  • Mazhar Ali

    • Max Planck Institute for Microstructure Physics
    • Max Plank Institute for Microstructure Physics
    • Max Planck Institute of Microstructure Physics