Dynamic Jahn-Teller viewpoint for generation mechanism of asymmetric modes of coherent phonons

Article

关键词: LIGHT-PULSES;    THZ PHONONS;    OSCILLATIONS;    SUPERCONDUCTIVITY;    DISPLACIVE;    EXCITATION;    STABILITY;    GAAS;   

DOI  :  10.1103/PhysRevB.95.104302

来源: SCIE

【 摘 要 】

We propose a dynamic Jahn-Teller approach to elucidate the generation mechanism of asymmetric modes of coherent phonons induced in crystals by irradiation with a short optical pulse in the opaque energy region. This is a natural extension of the impulsive excitation model of symmetric modes to multi dimensions in the configuration coordinate space. We show that the two generation mechanisms of coherent phonons coexist in this case, namely the impulsive absorption (IA) mechanism and impulsive stimulated Raman scattering (ISRS) mechanism. The dependence of the phonon amplitude on the polarization of the pump pulse is exactly the same in IA and ISRS processes and is in agreement with the prediction of the argument based on Raman tensors. The dependence of the excitation efficiency of the coherent phonons on the frequency of the pump pulse is calculated using a simplified model of the optical response function of the crystal. Generally, the IA mechanism predominates in the opaque region, although ISRS makes a comparable contribution to phonon generation in the near-edge opaque region. The initial phase of the coherent phonon is always cosine-like in IA but depends on the excitation frequency in ISRS.

【 授权许可】

Free