Vidal Franck, Zheng Yunlin, Lounis Lounès, Coelho Leticia, Laulhé Claire, Spezzani Carlo, Ciavardini Alessandra, Popescu Horia, Ferrari Eugenio, Allaria Enrico, Ma Jialin, Wang Hailong, Zhao Jianhua, Chollet Matthieu, Seaberg Matthew, Alonso-Mori Roberto, Glownia James M, Eddrief Mahmoud, Sacchi Maurizio
Sorbonne Université, CNRS, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
PSL Research University, 75231 Paris, France.
Phys Rev Lett. 2019 Apr 12;122(14):145702. doi: 10.1103/PhysRevLett.122.145702.
We investigate the orthorhombic distortion and the structural dynamics of epitaxial MnAs layers on GaAs(001) using static and time-resolved x-ray diffraction. Laser-induced intensity oscillations of Bragg reflections allow us to identify the optical phonon associated with orthorhombic distortion and to follow its softening along the path towards an undistorted phase of hexagonal symmetry. The frequency of this mode falls in the THz range, in agreement with recent calculations. Incomplete softening suggests that the β-γ transformation deviates from a purely second-order displacive transition.
我们使用静态和时间分辨X射线衍射研究了GaAs(001)上外延MnAs层的正交畸变和结构动力学。布拉格反射的激光诱导强度振荡使我们能够识别与正交畸变相关的光学声子，并跟踪其在向六方对称无畸变相转变过程中的软化情况。该模式的频率落在太赫兹范围内，与最近的计算结果一致。不完全软化表明β-γ转变偏离了纯粹的二级位移转变。
