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arXiv · 2110.00865

Role of equilibrium fluctuations in light-induced order

Alfred Zong·Pavel E. Dolgirev·Anshul Kogar·Yifan Su·Xiaozhe Shen·Joshua A. W. Straquadine·Xirui Wang·Duan Luo·Michael E. Kozina·Alexander H. Reid·Renkai Li·Jie Yang·Stephen P. Weathersby·Suji Park·Edbert J. Sie·Pablo Jarillo-Herrero·Ian R. Fisher·Xijie Wang·Eugene Demler·Nuh Gedik
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Abstract

Engineering novel states of matter with light is at the forefront of materials research. An intensely studied direction is to realize broken-symmetry phases that are "hidden" under equilibrium conditions but can be unleashed by an ultrashort laser pulse. Despite a plethora of experimental discoveries, the nature of these orders and how they transiently appear remain unclear. To this end, we investigate a nonequilibrium charge density wave (CDW) in rare-earth tritellurides, which is suppressed in equilibrium but emerges after photoexcitation. Using a pump-pump-probe protocol implemented in ultrafast electron diffraction, we demonstrate that the light-induced CDW consists solely of order parameter fluctuations, which bear striking similarities to critical fluctuations in equilibrium despite differences in the length scale. By calculating the dynamics of CDW fluctuations in a nonperturbative model, we further show that the strength of the light-induced order is governed by the amplitude of equilibrium fluctuations. These findings highlight photoinduced fluctuations as an important ingredient for the emergence of transient orders out of equilibrium. Our results further suggest that materials with strong fluctuations in equilibrium are promising platforms to host "hidden" orders after laser excitation.

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Alfred Zong, Pavel E. Dolgirev, Anshul Kogar, Yifan Su, Xiaozhe Shen, Joshua A. W. Straquadine, Xirui Wang, Duan Luo, Michael E. Kozina, Alexander H. Reid, Renkai Li, Jie Yang, Stephen P. Weathersby, Suji Park, Edbert J. Sie, Pablo Jarillo-Herrero, Ian R. Fisher, Xijie Wang, Eugene Demler, Nuh Gedik. 2021-10-02. Role of equilibrium fluctuations in light-induced order. https://doi.org/10.1103/physrevlett.127.227401

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