Observation of anomalous electron relaxation in optically excited 1T-TaSe2

ORAL

Abstract

Ultrafast light pulses can drive materials far from their equilibrium states and is a powerful approach for manipulating their states. The resultant multi-step energy and momentum relaxation processes can give us insight into the dominant interactions in these materials. In this work, we present a series of anomalous behaviors observed in the electron relaxation in the charge density wave (CDW) material 1T-TaSe2. After exciting the material with a femtosecond laser pulse, we measure the temporal evolution of the band structure and electron temperature. We observe a band oscillation that is coherently coupled to the CDW amplitude mode. Meanwhile, the hot electron temperature relaxes anomalously fast, and very different from that predicted by the widely-used N-temperature model. Moreover, this anomaly shows a critical change at the laser fluence corresponding to the ultrafast phase transformation to a new long-lived metastable state. These results offer a rare opportunity for better understanding of the coherent electron-phonon coupling.

–

Presenters

  • Yingchao Zhang

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

Authors

  • Yingchao Zhang

    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

  • Wenjing You

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

  • Zhensheng Tao

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

  • Kai Rossnagel

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

  • Michael Bauer

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

  • Henry C Kapteyn

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

  • Margaret Mary Murnane

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