"Dynamical Slowing-Down in an Ultrafast Photoinduced Phase Transition"

Alfred Zong: Pavel E. Dolgirev, Anshul Kogar, Emre Ergeçen, Mehmet B. Yilmaz, Ya-Qing Bie, Timm Rohwer, I-Cheng Tung, Joshua Straquadine, Xirui Wang, Yafang Yang, Xiaozhe Shen, Renkai Li, Jie Yang, Suji Park, Matthias C. Hoffmann, Benjamin K. Ofori-Okai, Michael E. Kozina, Haidan Wen, Xijie Wang, Ian R. Fisher, Pablo Jarillo-Herrero, and Nuh Gedik; Physical Review Letters, 08/29/19.

Additional Authors: Pavel E. Dolgirev, Anshul Kogar, Emre Ergeçen, Mehmet B. Yilmaz, Ya-Qing Bie, Timm Rohwer, I-Cheng Tung, Joshua Straquadine, Xirui Wang, Yafang Yang, Xiaozhe Shen, Renkai Li, Jie Yang, Suji Park, Matthias C. Hoffmann, Benjamin K. Ofori-Okai, Michael E. Kozina, Haidan Wen, Xijie Wang, Ian R. Fisher, Pablo Jarillo-Herrero, and Nuh Gedik

Abstract:

Complex systems, which consist of a large number of interacting constituents, often exhibit universal behavior near a phase transition. A slowdown of certain dynamical observables is one such recurring feature found in a vast array of contexts. This phenomenon, known as critical slowing-down, is well studied mostly in thermodynamic phase transitions. However, it is less understood in highly nonequilibrium settings, where the time it takes to traverse the phase boundary becomes comparable to the timescale of dynamical fluctuations. Using transient optical spectroscopy and femtosecond electron diffraction, we studied a photoinduced transition of a model charge-density-wave (CDW) compound LaTe3. We observed that it takes the longest time to suppress the order parameter at the threshold photoexcitation density, where the CDW transiently vanishes. This finding can be captured by generalizing the time-dependent Landau theory to a system far from equilibrium. The experimental observation and theoretical understanding of dynamical slowing-down may offer insight into other general principles behind nonequilibrium phase transitions in many-body systems.