Non-thermal hot electrons ultrafastly generating hot optical phonons in graphite

Investigation of the non-equilibrium dynamics after an impulsive impact provides insights into couplings among various excitations. A two-temperature model (TTM) is often a starting point to understand the coupled dynamics of electrons and lattice vibrations: the optical pulse primarily raises the e...

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Bibliographic Details
Published in:Scientific reports 2011-08, Vol.1 (1), p.64-64, Article 64
Main Authors: Ishida, Y., Togashi, T., Yamamoto, K., Tanaka, M., Taniuchi, T., Kiss, T., Nakajima, M., Suemoto, T., Shin, S.
Format: Article
Language:English
Subjects:
639/301
639/301/1019
639/301/119/995
Graphite
Humanities and Social Sciences
multidisciplinary
Science
Spectroscopy
Temperature effects
Vibrations
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Summary:Investigation of the non-equilibrium dynamics after an impulsive impact provides insights into couplings among various excitations. A two-temperature model (TTM) is often a starting point to understand the coupled dynamics of electrons and lattice vibrations: the optical pulse primarily raises the electronic temperature T el while leaving the lattice temperature T l low; subsequently the hot electrons heat up the lattice until T el = T l is reached. This temporal hierarchy owes to the assumption that the electron-electron scattering rate is much larger than the electron-phonon scattering rate. We report herein that the TTM scheme is seriously invalidated in semimetal graphite. Time-resolved photoemission spectroscopy (TrPES) of graphite reveals that fingerprints of coupled optical phonons (COPs) occur from the initial moments where T el is still not definable. Our study shows that ultrafast-and-efficient phonon generations occur beyond the TTM scheme, presumably associated to the long duration of the non-thermal electrons in graphite.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep00064