Valley Polarization and Coherence in WSe<sub>2</sub>-WTe<sub>2</sub> Alloys

ORAL

Abstract

Valleytronics is a driving motivation behind the exploration of transition metal dichalcogenides (TMDs). However, few studies have explored valley-dependent phenomena in TMD alloys. This is an important knowledge gap as the flexibility provided by alloying may be vital for the application of TMDs. We study the valleytronic properties of monolayer WSe2(1-x)Te2x (x=0…1), an alloy system where the endpoints WSe2 and WTe2 occupy different structural phases (H and 1T’, respectively). As the Te composition x is increased, the alloy undergoes a semiconductor-semimetal phase transition, which we explore with temperature-dependent Raman and photoluminescence (PL) measurements. We find that Te incorporation activates new Raman modes, while also leading to non-monotonic shifts in the neutral exciton and trion energies and linewidths. Temperature-dependent PL measurements show valley polarization and valley coherence survive when Te doping is less than ~23%, above which valley polarization disappears while valley coherence gradually decreases. These findings demonstrate that valleytronic properties can be robust against disorder and illustrate the potential of two-dimensional alloys for valleytronic technologies.

*This work is funded by NSF EAGER grant #1748650.

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Presenters

  • Sean Oliver

    • Department of Physics and Astronomy, George Mason University

Authors

  • Sean Oliver

    • Department of Physics and Astronomy, George Mason University

  • Joshua Young

    • Department of Physics, Applied Physics and Astronomy, Binghamton University

  • Sergiy Krylyuk

    • Functional Nanostructured Materials Group, National Institute of Standards and Technology
    • Functional Nanostructured Materials Group, NIST
    • NIST

  • Amber McCreary

    • Nanoscale Spectroscopy Group, National Institute of Standards and Technology
    • Engineering Physics Division, National Institute of Standards and Technology

  • Angela Hight Walker

    • NIST
    • Nanoscale Device Characterization Division, National Institute of Standards and Technology
    • National Institute of Standards and Technology
    • Nanoscale Device Characterization Division, Physical Measurement Laboratory, National Institute of Standards and Technology
    • Nanoscale Spectroscopy Group, National Institute of Standards and Technology
    • Engineering Physics Division, National Institute of Standards and Technology

  • Thomas Reinecke

    • United States Naval Research Laboratory
    • Quantum Phenomena and Modeling Section, Naval Research Laboratory

  • Albert Davydov

    • Functional Nanostructured Materials Group, National Institute of Standards and Technology
    • Functional Nanostructured Materials Group, NIST

  • Patrick Vora

    • George Mason Univ
    • Department of Physics and Astronomy, George Mason University
    • George Mason University