Distinct ultrafast carrier dynamics governed by spin filtering in bulk and single-layer WSe<sub>2</sub>

ORAL

Abstract

Carrier dynamics in a semiconductor following pulsed optical excitation is relevant to ultrafast optoelectronic applications. We report herein a comparative study of bulk WSe2 and single-layer (SL) WSe2 grown on bilayer-graphene-terminated SiC. Subtle dimensional effects lead to substantial differences in the transient response as revealed by time-resolved angle-resolved photoemission spectroscopy (TRARPES) measurements. The conduction band minimum in bulk WSe2, populated by optical pumping, decays promptly. The corresponding decay for SL WSe2 is more complex but overall much slower due to spin filtering arising from the lack of space inversion symmetry. Concurrent measurements of the valence bands show longer but different response times arising from lattice excitation, carrier transport, and dissipation. These results illustrate the various time scales and processes at work for carrier and band structure evolution.

*This work is supported by the U.S. DOE, Office of Science, Office of Basic Energy Sciences, Division of Materials Science and Engineering, under Grant No. DE-FG02-07ER46383 (TCC). The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

–

Presenters

  • Ro-Ya Liu

    • University of Illinois at Urbana-Champaign
    • Institute of Physics, Academia Sinica
    • Department of Physics, University of Illinois-Urbana-Champaign

Authors

  • Ro-Ya Liu

    • University of Illinois at Urbana-Champaign
    • Institute of Physics, Academia Sinica
    • Department of Physics, University of Illinois-Urbana-Champaign

  • Meng-Kai Lin

    • Department of Physics, University of Illinois Urbana-Champaign
    • University of Illinois at Urbana-Champaign
    • Physics, University of Illinois at Urbana-Champaign
    • Department of Physics, University of Illinois-Urbana-Champaign

  • Peng Chen

    • Physics, University of Illinois at Urbana-Champaign
    • Department of Physics, University of Illinois-Urbana-Champaign

  • Takeshi Suzuki

    • Institute for Solid State Physics, University of Tokyo

  • Philippa Clark

    • Photon Science Institute, University of Manchester

  • Nathan Lewis

    • Photon Science Institute, University of Manchester

  • Cephise Cacho

    • Diamond Light Source, STFC Rutherford Appleton Laboratory

  • Emma Springate

    • Central Laser Facility, STFC Rutherford Appleton Laboratory

  • Chia-Seng Chang

    • Institute of Physics, Academia Sinica, Taipei, Taiwan
    • Institute of Physics, Academia Sinica

  • Kozo Okazaki

    • Institute for Solid State Physics, University of Tokyo
    • Institute for Solid State Physics, The University of Tokyo

  • Wendy Flavell

    • Photon Science Institute, University of Manchester

  • Iwao Matsuda

    • Institute for Solid State Physics, University of Tokyo

  • Tai-Chang Chiang

    • University of Illinois at Urbana-Champaign
    • Physics, University of Illinois
    • Department of Physics, University of Illinois Urbana-Champaign
    • Physics, University of Illinois at Urbana-Champaign
    • Department of Physics, University of Illinois-Urbana-Champaign
    • Physics, University of Illinois Urbana-Champaign