Observation of photo-induced plasmon-phonon coupling in PbTe via ultrafast x-ray scattering

M P Jiang; S Fahy; A Hauber; É D Murray; I Savić; C Bray; J N Clark; T Henighan; M Kozina; A M Lindenberg; P Zalden; M Chollet; J M Glownia; M C Hoffmann; T Sato; D Zhu; O Delaire; A F May; B C Sales; R Merlin; M Trigo; D A Reis

doi:10.1063/4.0000133

Observation of photo-induced plasmon-phonon coupling in PbTe via ultrafast x-ray scattering

Struct Dyn. 2022 Mar 14;9(2):024301. doi: 10.1063/4.0000133. eCollection 2022 Mar.

Authors

M P Jiang, S Fahy¹, A Hauber¹, É D Murray, I Savić¹, C Bray, J N Clark², T Henighan, M Kozina, A M Lindenberg, P Zalden, M Chollet³, J M Glownia³, M C Hoffmann³, T Sato³, D Zhu³, O Delaire⁴, A F May⁵, B C Sales⁵, R Merlin⁶, M Trigo, D A Reis

Affiliations

¹ Tyndall National Institute and Department of Physics, University College, Cork, Ireland.
² Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
³ Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
⁴ Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA.
⁵ Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
⁶ Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.

Abstract

We report the observation of photo-induced plasmon-phonon coupled modes in the group IV-VI semiconductor PbTe using ultrafast x-ray diffuse scattering at the Linac Coherent Light Source. We measure the near-zone-center excited-state dispersion of the heavily screened longitudinal optical (LO) phonon branch as extracted from differential changes in x-ray diffuse scattering intensity following above bandgap photoexcitation. We suggest that upon photoexcitation, the LO phonon-plasmon coupled (LOPC) modes themselves become coupled to longitudinal acoustic modes that drive electron band shifts via acoustic deformation potentials and possibly to low-energy single-particle excitations within the plasma and that these couplings give rise to displacement-correlations that oscillate in time with a period given effectively by the heavily screened LOPC frequency.