Coherent phonons and the interplay between charge density wave and Mott phases in 1<i>T</i>-TaSe<sub>2</sub>

ORAL

Abstract

1T-TaSe2 is an ideal system in which to explore the phenomenon of coexisting order since it is host to both a charge density wave (CDW) and Mott phase at low temperature. We investigated the CDW-Mott phase in 1T-TaSe2 at 77 K using a combination of time- and angle-resolved photoemission spectroscopy (TR-ARPES) and time-resolved reflectivity (TRR) which reveals strong coherent phonon oscillations [1]. Most importantly, we find that perturbation using a femtosecond laser pulse in TR-ARPES triggers a modulation of the Mott gap with a single frequency related to the in-plane CDW amplitude mode, whereas TRR measurements show a modulation comprised of multiple frequencies belonging to the distorted CDW lattice modes. Our results clearly identify the relationship of the in-plane CDW amplitude mode with the Mott phase in 1T-TaSe2 and highlight the importance of lattice degrees of freedom.

[1] C. J. Sayers et al. Phys. Rev. B. 102, 161105(R) (2020)

*The authors acknowledge funding from EPSRC Grant No. EP/L015544/1 and the Italian PRIN Project No. 2017BZPKSZ.

–

Presenters

  • Charles Sayers

    • University of Bath
    • Politecnico di Milano

Authors

  • Charles Sayers

    • University of Bath
    • Politecnico di Milano

  • Hamoon Hedayat

    • Politecnico di Milano

  • Ariana Ceraso

    • Politecnico di Milano

  • Flavien Museur

    • Université de Lyon

  • Mattia Cattelan

    • University of Bristol

  • Lewis Hart

    • University of Bath

  • Liam Farrar

    • University of Bath

  • Stefano Dal Conte

    • Physics, Politecnico di Milano
    • Politecnico di Milano

  • Giulio Cerullo

    • Dipartimento di Fisica, Politecnico di Milano
    • Physics, Politecnico di Milano
    • Politecnico di Milano

  • Claudia Dallera

    • Politecnico di Milano

  • Enrico Da Como

    • University of Bath

  • Ettore Carpene

    • Politecnico di Milano