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

作者：Ishida Y^*; Togashi T; Yamamoto K; Tanaka M; Taniuchi T; Kiss T; Nakajima M; Suemoto T; Shin S

来源：Scientific Reports, 2011, 1(1): 64.

DOI：10.1038/srep00064

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.

• 出版日期2011-8-19