Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Phys Rev Lett. 2018 Sep 21;121(12):125901. doi: 10.1103/PhysRevLett.121.125901.
We report channel-resolved measurements of the anharmonic coupling of the coherent A_{1g} phonon in photoexcited bismuth to pairs of high wave vector acoustic phonons. The decay of a coherent phonon can be understood as a parametric resonance process whereby the atomic displacement periodically modulates the frequency of a broad continuum of modes. This coupling drives temporal oscillations in the phonon mean-square displacements at the A_{1g} frequency that are observed across the Brillouin zone by femtosecond x-ray diffuse scattering. We extract anharmonic coupling constants between the A_{1g} and several representative decay channels that are within an order of magnitude of density functional perturbation theory calculations.
我们报告了在光激发下铋中相干 A_{1g}声子与高波矢声子对的非谐耦合的通道分辨测量。相干声子的衰减可以理解为一个参量共振过程，其中原子位移周期性地调制宽连续模式的频率。这种耦合在布里渊区中通过飞秒 X 射线漫散射观察到在 A_{1g}频率下的声子均方位移的时间振荡。我们提取了 A_{1g}和几个代表性衰减通道之间的非谐耦合常数，它们与密度泛函微扰理论计算在数量级上相符。
