Observation of a Novel Lattice Instability in Ultrafast Photoexcited SnSe oleh Yijing Huang, Shan Yang, Samuel Teitelbaum, Gilberto De la Peña, Takahiro Sato, Matthieu Chollet, Diling Zhu, Jennifer L. Niedziela, Dipanshu Bansal, Andrew F. May, Aaron M. Lindenberg, Olivier Delaire, David A. Reis, Mariano Trigo