Dynamical Birefringence: Electron-Hole Recollisions as Probes of Berry Curvature
Dynamical Birefringence: Electron-Hole Recollisions as Probes of Berry Curvature
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DOI：
10.1103/physrevx.7.041042
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发表时间：
2017-11-21
影响因子：
12.5
通讯作者：
Sherwin, Mark S.
中科院分区：
文献类型：
--
作者：
Banks, Hunter B.;Wu, Qile;Sherwin, Mark S.
在凝聚态系统中直接测量Berry相仍然是一个很大的挑战。瓶颈一直是在散射强烈而复杂的固体中相干地驱动电子穿过布里渊区的大部分的能力。我们突破了这一瓶颈，并表明，高阶边带产生（HSG）在半导体是密切影响贝里相位。当近带隙激光束激发由足够强的太赫兹频率电场驱动的半导体时，会发生电子空穴碰撞和HSG。我们对三个GaAs/AlGaAs量子威尔斯阱的HSG进行了实验和理论研究。所观察到的HSG光谱包含的边带高达90阶，据我们所知，最高阶的固体中的光学非线性报道。最高阶边带与在伽马点周围的布里渊区的大约10%上相干驱动的电子-空穴对相关联。主要的实验要求是动态双折射：边带的强度和偏振取决于激发近红外（NIR）和太赫兹电场的相对偏振，以及激光场与晶体的相对取向。我们解释动力学双折射的三步模型概括的高次谐波产生。在太赫兹场下，由于准动量的变化，空穴的内部状态发生变化，从而积累了Berry相位。动力学双折射是由时间反演的电子-空穴碰撞路径对之间的量子干涉引起的。提出了一种利用动态双折射测量固体中Berry曲率的方法。
The direct measurement of Berry phases is still a great challenge in condensed-matter systems. The bottleneck has been the ability to adiabatically drive an electron coherently across a large portion of the Brillouin zone in a solid where the scattering is strong and complicated. We break through this bottleneck and show that high-order sideband generation (HSG) in semiconductors is intimately affected by Berry phases. Electron-hole recollisions and HSG occur when a near-band-gap laser beam excites a semiconductor that is driven by sufficiently strong terahertz-frequency electric fields. We carry out experimental and theoretical studies of HSG from three GaAs/AlGaAs quantum wells. The observed HSG spectra contain sidebands up to the 90th order, to our knowledge the highest-order optical nonlinearity reported in solids. The highest-order sidebands are associated with electron-hole pairs driven coherently across roughly 10% of the Brillouin zone around the Gamma point. The principal experimental claim is a dynamical birefringence: the intensity and polarization of the sidebands depend on the relative polarization of the exciting near-infrared (NIR) and the THz electric fields, as well as on the relative orientation of the laser fields with the crystal. We explain dynamical birefringence by generalizing the three-step model for high-order harmonic generation. The hole accumulates Berry phases due to variation of its internal state as the quasimomentum changes under the THz field. Dynamical birefringence arises from quantum interference between time-reversed pairs of electron-hole recollision pathways. We propose a method to use dynamical birefringence to measure Berry curvature in solids.