30 research outputs found
Exciton Mott transition in Si Revealed by Terahertz Spectroscopy
Exciton Mott transition in Si is investigated by using terahertz time-domain
spectroscopy. The excitonic correlation as manifested by the 1s-2p resonance is
observed above the Mott density. The scattering rate of charge carriers is
prominently enhanced at the proximity of Mott density, which is attributed to
the non-vanishing exciton correlation in the metallic electron-hole plasma.
Concomitantly, the signature of plasmon-exciton coupling is observed in the
loss function spectra.Comment: 5 pages, 3 figure
Cooling Dynamics of Photoexcited Carriers in Si Studied by Using Optical Pump and Terahertz Probe Spectroscopy
We investigated the photoexcited carrier dynamics in Si by using optical pump
and terahertz probe spectroscopy in an energy range between 2 meV and 25 meV.
The formation dynamics of excitons from unbound e-h pairs was studied through
the emergence of the 1s-2p transition of excitons at 12 meV (3 THz). We
revealed the thermalization mechanism of the photo-injected hot carriers
(electrons and holes) in the low temperature lattice system by taking account
of the interband and intraband scattering of carriers with acoustic and optical
phonons. The overall cooling rate of electrons and holes was numerically
calculated on the basis of a microscopic analysis of the phonon scattering
processes, and the results well account for the experimentally observed carrier
cooling dynamics. The long formation time of excitons in Si after the above-gap
photoexcitation is reasonably accounted for by the thermalization process of
photoexcited carriers.Comment: 8 pages, 8 figures, to be published in Phys. Rev.