Direct determination of mode-projected electron-phonon coupling in the time domain

Na, M. X.
Mills, A. K.
Boschini, F.
Michiardi, M.
Nosarzewski, B.
Day, R. P.
Razzoli, E.
Sheyerman, A.
Schneider, M.
Levy, G.
Zhdanovich, S.
Devereaux, T. P.
Kemper, A. F.
Jones, D. J.
Damascelli, A.

¹Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
²Quantum Matter Institute, Vancouver, BC V6T 1Z4, Canada.
³Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
⁴Department of Materials Science and Engineering, Stanford Institute for Materials and Energy Sciences, Stanford, CA 94305, USA.
⁵Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.

* These authors contributed equally to this work.

Corresponding author. Email: [email protected] (D.J.J.); [email protected] (A.D.)

Received November 23, 2018

Accepted November 05, 2019

Science 366(6470):p 1231-1236, December 06, 2019. | DOI: 10.1126/science.aaw1662

Ultrafast spectroscopies have become an important tool for elucidating the microscopic description and dynamical properties of quantum materials. In particular, by tracking the dynamics of nonthermal electrons, a material’s dominant scattering processes can be revealed. Here, we present a method for extracting the electron-phonon coupling strength in the time domain, using time- and angle-resolved photoemission spectroscopy (TR-ARPES). This method is demonstrated in graphite, where we investigate the dynamics of photoinjected electrons at the K point, detecting quantized energy-loss processes that correspond to the emission of strongly coupled optical phonons. We show that the observed characteristic time scale for spectral weight transfer mediated by phonon-scattering processes allows for the direct quantitative extraction of electron-phonon matrix elements for specific modes.