Raman Signatures of Charge Density Waves in 2H-TaS2

ORAL

Abstract

Many group V transition metal dichalcogenides (TMDs) exhibit quantum phase transitions from a metallic state to a charge density wave (CDW) state at low temperatures. Strong electron-phonon interactions drive this transition, and therefore knowledge of the phonon modes in the CDW state is important for understanding this phenomenon. 2H-TaS2 is known to undergo a CDW transition at ~75 K based on electrical and magnetic measurements, however studies of this transition using optical methods, especially Raman, are limited.1 We perform a comprehensive study of the metal-to-CDW transition in bulk 2H-TaS2 capped with hexagonal boron nitride (h-BN) by combining temperature, polarization, and excitation-dependent Raman spectroscopy. Using quasi-resonant excitation, we observe three optical modes associated with the CDW phase and their symmetries, of which the feature at 65 cm-1 is previously unreported. Temperature-dependent studies confirm the correlation of the mode intensities to the CDW transition and we estimate the strength of the electron-phonon coupling parameter by extracting the CDW mode frequencies and their linewidths. These results lay the foundation for future explorations of layer-dependent CDW physics in 2H-TaS2.
(1) Sugai, S., et al. Solid State Commun. 1981, 40, 399–401.

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Presenters

  • Jaydeep Joshi

    Departments of Physics and Astronomy, George Mason University, Physics and Astronomy, George Mason University

Authors

  • Jaydeep Joshi

    Departments of Physics and Astronomy, George Mason University, Physics and Astronomy, George Mason University

  • Heather Hill

    Engineering Physics, National Institute of Standards and Technology, National Institute of Standards and Technology, Physical Measurements Laboratory, National Institute of Standards and Technology, Physical Measurment Division, NIST, NIST -Natl Inst of Stds & Tech, NIST - National Institute of Standards and Technology

  • Christos Malliakas

    Department of Chemistry, Northwestern University, Department of Chemistry, Northwestern Univesity

  • Utpal Chatterjee

    University of Virginia, Department of Physics, University of Virginia, Department of Physics, University of Virgina, Physics, Univ of Virginia

  • Angela Hight Walker

    Engineering Physics, National Institute of Standards and Technology, National Institute of Standards and Technology, NIST - Natl Inst of Stds & Tech, Physical Measurements Laboratory, National Institute of Standards and Technology, Physical Measurment Division, NIST, NIST -Natl Inst of Stds & Tech, Physical Measurement Laboratory, National Institute of Standards and Technology, NIST - National Institute of Standards and Technology, National Institute of Standards and Technology (NIST), National Institute of Standards & Technology

  • Patrick Vora

    George Mason University, Departments of Physics and Astronomy, George Mason University, Physics and Astronomy, George Mason University