Absence of amplitude mode softening of intermediate states in the charge density wave material 1<i>T</i>-TaSe<sub>2</sub>

ORAL

Abstract

Recently, we uncovered new long-lived metastable charge density wave (CDW) states in 1T-TaSe2 that are launched by an ultrafast laser pulse [1]. Moreover, the transitions from CDW to metastable to normal phases exhibit second order phase transition behaviors with continuously tunable order parameters, although it is a first order transition under thermal-equilibrium conditions. Ultrafast light-induced phase transitions thus extend the phase diagram of strongly-coupled materials, allowing us to access new states which are unreachable by chemical doping or by varying the temperature. In order to further understand the nature of these new metastable intermediate states, a second weak pump pulse is applied to probe their properties. Surprisingly, the CDW amplitude mode frequency of all intermediate states (between the CDW and normal states) is the same as that of CDW state - and vanishes only when the material reaches the normal state. This abrupt change of phonon mode frequency, reveals an exotic interatomic potential that may be intrinsic to the first-order nature of the phase transition in equilibrium. Our results provide new insight in understanding the formation and nature of ultrafast laser- induced metastable states.
[1] Science Advances 5, eaav4449 (2019).

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Presenters

  • Wenjing You

    • JILA, University of Colorado Boulder
    • Department of Physics and JILA, University of Colorado, Boulder
    • University of Colorado, Boulder

Authors

  • Wenjing You

    • JILA, University of Colorado Boulder
    • Department of Physics and JILA, University of Colorado, Boulder
    • University of Colorado, Boulder

  • Xun Shi

    • JILA, University of Colorado Boulder
    • Department of Physics and JILA, University of Colorado, Boulder
    • University of Colorado, Boulder

  • Yingchao Zhang

    • JILA, University of Colorado Boulder
    • Department of Physics and JILA, University of Colorado, Boulder
    • University of Colorado, Boulder

  • Yigui Zhong

    • Department of Physics and JILA, University of Colorado, Boulder
    • University of Colorado, Boulder

  • Zhensheng Tao

    • Department of Physics and JILA, University of Colorado, Boulder
    • University of Colorado, Boulder

  • Michael Bauer

    • Institute of Experimental and Applied Physics, Kiel University
    • University of Kiel
    • Kiel University

  • Kai Rossnagel

    • Christian-Albrechts-Universitat zu Kiel
    • Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
    • Institute of Experimental and Applied Physics, Kiel University
    • Kiel University
    • University of Kiel

  • Henry Kapteyn

    • JILA, University of Colorado Boulder
    • Department of Physics and JILA, University of Colorado, Boulder
    • STROBE and JILA, University of Colorado, Boulder
    • JILA and Department of Physics, University of Colorado, Boulder
    • STROBE and JILA, University of Colorado and NIST
    • Physics, JILA/University of Colorado Boulder
    • JILA
    • University of Colorado, Boulder
    • Physics and JILA, CU Boulder
    • JILA, University of Colorado, Boulder

  • Margaret Murnane

    • JILA, University of Colorado Boulder
    • Department of Physics and JILA, University of Colorado, Boulder
    • STROBE and JILA, University of Colorado, Boulder
    • STROBE and JILA, University of Colorado and NIST
    • JILA
    • University of Colorado, Boulder
    • Physics and JILA, CU Boulder
    • University of Colorado
    • JILA, University of Colorado, Boulder