Non-equilibrium dynamics of the phonon system (B04)

利用飞秒时间分辨率的超快电子衍射，研究了声子在光激发下在晶体薄膜及其表面的激发、衰减和输运。我们着重于通过电子态、应变态、表面和界面粗糙度的变化来操纵电子声子耦合，从而通过形成压缩态、表面态的e-ph耦合或非谐波ph-ph耦合来控制晶格的振动激发。我们通过从扩散到弹道声子输运的转换，迫使声子系统违反均分。

The excitation, decay, and transport of phonons in crystalline films and at their surfaces upon an optical excitation will be studied by ultrafast electron diffraction with femtosecond temporal resolution. We focus on the manipulation of electron phonon coupling through variation of electronic states, strain state, surface and interface roughness and thus control the vibrational excitation of lattice through either formation of squeezed state, e-ph coupling through surface state, or anharmonic ph-ph coupling. We force violation of equipartition in the phonon system through switching from diffusive to ballistic phonon transport.