Transient responses of the electronic excitation and coherent soft phonon are investigated both above and below the ferroelectric phase transition temperature T$_{ c}$ in Pb$_{ 1-x}$Ge$_{ x}$Te by using an optical pump-probe technique. The coherent soft mode shows large red-shift and heavily over-damped decay as the temperature approaching T$_{ c}$ from the low temperature side and the soft mode disappears above T$_{ c}$. The transient electronic response exhibits an abrupt change across T$_{ c}$. The critical behaviors of both the phononic and electronic dynamics are interpreted by the ferroelectric phase transition.
Categories: cond-mat.mtrl-sci