Dynamic Fano Resonance and Transient Quasiparticle Generation in Semiconductors Excited by Ultrashort Pulse Laser

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Irradiation of semiconductor with intense and ultrashort pulse-laser leads to instantaneous generation of on-phase collective motion of phonon termed coherent phonon, which shows pronounced vibrational patterns in observables. The present study is aimed at establishing a quantum-theoretical framework that makes it possible to interpret transient Fano resonance and a coupled state of LO phonon with plasmon in a unified manner, both phenomena of which are accompanied by the CP generation. Further, based on this framework, one intends to examine the experimental results. For this purpose, a polaronic quasiparticle picture is proposed, where the associated quasiboson operator is composed of the operators of plasmon, electron-hole pair, and phonon. In particular, this framework is applied to the CP generation accompanying the transient Fano resonance, and one has succeeded in obtaining an analytic expression well reproducing this effect.