Ultrafast Critical Dynamics of Ferroelectric Phase Transition in Pb$_{1-x}$Ge$_{x}$Te

TL;DR

This study investigates the ultrafast electronic and phononic responses of Pb$_{1-x}$Ge$_{x}$Te across its ferroelectric phase transition, revealing critical dynamics and mode behavior near T$_{c}$ using pump-probe spectroscopy.

Contribution

It provides new insights into the critical dynamics of ferroelectric phase transitions through ultrafast optical measurements of both electronic and phononic responses.

Findings

Coherent soft mode shows large red-shift near T$_{c}$.

Soft mode becomes over-damped and disappears above T$_{c}$.

Electronic response exhibits an abrupt change at T$_{c}$.

Abstract

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.