"Spatial Distortion of Vibration Modes via Magnetic Correlation of Impurities"

F. S. Krasniqi: Y. Zhong, S. W. Epp, L. Foucar, M. Trigo, J. Chen, D. A. Reis, H. L. Wang, J. H. Zhao, H. T. Lemke, D. Zhu, M. Chollet, D. M. Fritz, R. Hartmann, L. Englert, L. Strüder, I. Schlichting, and J. Ullrich; Phys. Rev. Lett, 03/08/18.

Additional Authors: Y. Zhong, S. W. Epp, L. Foucar, M. Trigo, J. Chen, D. A. Reis, H. L. Wang, J. H. Zhao, H. T. Lemke, D. Zhu, M. Chollet, D. M. Fritz, R. Hartmann, L. Englert, L. Strüder, I. Schlichting, and J. Ullrich

Abstract:

Long wavelength vibrational modes in the ferromagnetic semiconductor Ga0.91Mn0.09As are investigated using time resolved x-ray diffraction. At room temperature, we measure oscillations in the x-ray diffraction intensity corresponding to coherent vibrational modes with well-defined wavelengths. When the correlation of magnetic impurities sets in, we observe the transition of the lattice into a disordered state that does not support coherent modes at large wavelengths. Our measurements point toward a magnetically induced broadening of long wavelength vibrational modes in momentum space and their quasilocalization in the real space. More specifically, long wavelength vibrational modes cannot be assigned to a single wavelength but rather should be represented as a superposition of plane waves with different wavelengths. Our findings have strong implications for the phonon-related processes, especially carrier-phonon and phonon-phonon scattering, which govern the electrical conductivity and thermal management of semiconductor-based devices.