Murray Éamonn D, Fahy Stephen
Tyndall National Institute, Cork, Ireland.
Tyndall National Institute, Cork, Ireland and Department of Physics, University College Cork, Cork, Ireland.
Phys Rev Lett. 2015 Feb 6;114(5):055502. doi: 10.1103/PhysRevLett.114.055502. Epub 2015 Feb 4.
We present a first-principles method for the calculation of the polarization-dependent atomic forces resulting from optical excitation in a solid. We calculate the induced force driving the E(g) phonon mode in bismuth immediately after absorption of polarized light. When radiation with polarization perpendicular to the c axis is absorbed, the photoexcited charge density breaks the threefold rotational symmetry, leading to an atomic force component perpendicular to the axis. We calculate the initial excited electronic distribution as a function of photon energy and polarization and find the resulting atomic force components parallel and perpendicular to the axis. The magnitude of the calculated force is in excellent agreement with that derived from recent measurements of the amplitude of E(g) atomic motion and the decay time of several femtoseconds for the driving force.
我们提出了一种基于第一性原理的方法，用于计算固体中光激发产生的与极化相关的原子力。我们计算了铋吸收偏振光后立即驱动E(g)声子模的感应力。当吸收偏振方向垂直于c轴的辐射时，光激发电荷密度打破了三重旋转对称性，导致产生一个垂直于该轴的原子力分量。我们计算了作为光子能量和极化函数的初始激发电子分布，并找到了与该轴平行和垂直的原子力分量。计算得到的力的大小与最近从E(g)原子运动幅度的测量以及驱动力的几个飞秒衰减时间推导得出的结果非常吻合。
