Magneto-Raman Spectroscopy of Layered Transition-Metal Dichalcogenides

ORAL

Abstract

Raman spectroscopy offers a non-contact, non-destructive, and high-throughput optical technique to probe the fundamental physics of two-dimensional (2D) layered materials. We discuss our unique magneto-Raman capability, which affords measurement of Raman spectra with simultaneous variation of temperature (4K to 400K), laser excitation wavelength (tunability from UV to near-IR), and magnetic field (up to 9 T). Coupling to a triple-grating spectrometer provides measurement of low-frequency phonons. Recent results on novel 2D materials will be presented to highlight instrumentation capabilities, including metallic TaSe2, which exhibits transitions between commensurate and incommensurate charge-density wave (CDW) phases, and related, layered materials. The dependence of the observed Raman-active phonons in TaSe2 on temperature and magnetic field will be presented and compared with earlier results on MoS2 and calculations using density functional theory. Specifically, we observe the appearance of low-frequency, zone-folded modes in the CDW state. The phase, amplitude, and previously unanalyzed zone-folding modes are assigned to specific phonons observed in experimental spectra and DFT. Uniquely, the calculations show Ta-rich stripes emerge in the commensurate CDW phase.

–

Presenters

  • Jeffrey Simpson

    Towson University, Physics, Astronomy and Geosciences, Towson University

Authors

  • Jeffrey Simpson

    Towson University, Physics, Astronomy and Geosciences, Towson University

  • Heather M. Hill

    NIST, National Institute of Standards and Technology

  • Sugata Chowdhury

    NIST, National Institute of Standards and Technology

  • Francesca Tavazza

    NIST, MML, National institute of standards and technology, MD, USA, Materials Measurment Laboratory, 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