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Ultrafast Structural Dynamics along the β-γ Phase Transition Path in MnAs
Franck Vidal1, Yunlin Zheng1, Lounès Lounis1,2
1Sorbonne Université, CNRS, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
Abstract:
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.
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