Coherent Phonon Generation from Prethermal Carrier Populations in a Semiconductor
Abstract
Ultrafast laser excitation of carriers in semiconductors often results in the creation of fully symmetric coherent optical phonons, typically understood in terms of a thermalized transient carrier population. We test this understanding with systematic measurements and first-principles calculations of the photon-energy dependence of ultrafast-laser-driven coherent phonon generation in tellurium, using excitation wavelengths around the electronic band gap. We observe that, contrary to the expectations of models assuming a thermalized carrier population, the coherent amplitude of the fully symmetric A1 mode changes only weakly when tuning wavelength across the band gap. The measured spectral dependence is instead reproduced by a transition-resolved prethermal force weighted by optical matrix elements and band- and momentum-dependent A1 deformation potentials. Fitting this model to the data yields an excited transition state lifetime of a few femtoseconds. These results identify transition selectivity, rather than a thermalized total carrier density, as a key factor controlling coherent-phonon generation in semiconductors excited near a band gap.
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BibTeX
@misc{shi2026coherent,
title = {{Coherent Phonon Generation from Prethermal Carrier Populations in a Semiconductor}},
author = {Mingyu Shi and Matteo Savoini and Patrick Friebel and Andrea Annunziata and Thomas Metzger and Yunpei Deng and Laura Cattaneo and Steven L. Johnson},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18279},
eprint = {2610.18279},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18279},
}
RIS
TY - UNPB
TI - Coherent Phonon Generation from Prethermal Carrier Populations in a Semiconductor
AU - Mingyu Shi
AU - Matteo Savoini
AU - Patrick Friebel
AU - Andrea Annunziata
AU - Thomas Metzger
AU - Yunpei Deng
AU - Laura Cattaneo
AU - Steven L. Johnson
PY - 2026
DA - 2026/10/25
PB - arXiv
DO - 10.48550/arxiv.2610.18279
UR - https://arxiv.org/abs/2610.18279
AB - Ultrafast laser excitation of carriers in semiconductors often results in the creation of fully symmetric coherent optical phonons, typically understood in terms of a thermalized transient carrier population. We test this understanding with systematic measurements and first-principles calculations of the photon-energy dependence of ultrafast-laser-driven coherent phonon generation in tellurium, using excitation wavelengths around the electronic band gap. We observe that, contrary to the expectations of models assuming a thermalized carrier population, the coherent amplitude of the fully symmetric A_1 mode changes only weakly when tuning wavelength across the band gap. The measured spectral dependence is instead reproduced by a transition-resolved prethermal force weighted by optical matrix elements and band- and momentum-dependent A_1 deformation potentials. Fitting this model to the data yields an excited transition state lifetime of a few femtoseconds. These results identify transition selectivity, rather than a thermalized total carrier density, as a key factor controlling coherent-phonon generation in semiconductors excited near a band gap.
ER -