Abstract:Pump-probe spectroscopies have extended many well-established equilibrium techniques into the time domain. Among them, time-resolved ARPES is especially exciting, as it provides access to the electronic structure and many-body interactions on an ultrafast timescale. Despite its success, the applicability of TR-ARPES has been curtailed by the limited photon energy, resolution, and repetition rate of available laser sources, which generally confine experiments to the low-momentum, high-fluence regime. At UBC, we have developed a new cavity-based high-harmonic ultrafast laser source that enables detailed, low-fluence TR-ARPES studies over the full Brillouin zone of quantum materials.
We apply this source to the study of electron-phonon coupling on graphite, a well-studied test subject. While many experimental techniques are sensitive to electron-phonon coupling, the measured quantity is usually averaged over electron degrees of freedom or bosonic degrees of freedom. In contrast, we observe quantized energy-loss processes that correspond to the emission of strongly coupled optical phonons, which allow for the quantitative extraction of the mode-projected electron-phonon matrix element, for specific initial and final electron states.
The features that we observe come from the non-thermal occupation of electrons. In high-fluence experiments, electron dynamics are often described by the evolution of the temperature, which masks the underlying microscopic scattering processes that are rich with information. Using the study of graphite as a benchmark, we use numerical simulations to elucidate non-thermal regimes at high and flow fluences, and further highlight the need for detailed perturbative experiments to exploit non-equilibrium electron properties in materials.
Biosketch:MengXing Na is an experimental condensed matter physicist. she is currently a PhD student, studying in the group of Andrea Damascelli and David J. Jones. Her work focusses on electron-phonon coupling and electron dynamics, which she studies using a combination of time and angle-resolved photoelectron spectroscopy and numerical simulation.
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2020-05-14T14:00:002020-05-14T15:00:00Determining electron-phonon coupling using time- and angle-resolved photoemission spectroscopyEvent Information:
Abstract: Pump-probe spectroscopies have extended many well-established equilibrium techniques into the time domain. Among them, time-resolved ARPES is especially exciting, as it provides access to the electronic structure and many-body interactions on an ultrafast timescale. Despite its success, the applicability of TR-ARPES has been curtailed by the limited photon energy, resolution, and repetition rate of available laser sources, which generally confine experiments to the low-momentum, high-fluence regime. At UBC, we have developed a new cavity-based high-harmonic ultrafast laser source that enables detailed, low-fluence TR-ARPES studies over the full Brillouin zone of quantum materials.
We apply this source to the study of electron-phonon coupling on graphite, a well-studied test subject. While many experimental techniques are sensitive to electron-phonon coupling, the measured quantity is usually averaged over electron degrees of freedom or bosonic degrees of freedom. In contrast, we observe quantized energy-loss processes that correspond to the emission of strongly coupled optical phonons, which allow for the quantitative extraction of the mode-projected electron-phonon matrix element, for specific initial and final electron states.
The features that we observe come from the non-thermal occupation of electrons. In high-fluence experiments, electron dynamics are often described by the evolution of the temperature, which masks the underlying microscopic scattering processes that are rich with information. Using the study of graphite as a benchmark, we use numerical simulations to elucidate non-thermal regimes at high and flow fluences, and further highlight the need for detailed perturbative experiments to exploit non-equilibrium electron properties in materials.
Biosketch: MengXing Na is an experimental condensed matter physicist. she is currently a PhD student, studying in the group of Andrea Damascelli and David J. Jones. Her work focusses on electron-phonon coupling and electron dynamics, which she studies using a combination of time and angle-resolved photoelectron spectroscopy and numerical simulation.Event Location:
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