量子动力学方程的非线性光学响应
Nonlinear optical response from quantum kinetic equation
摘要：
受拓扑半金属中观察到的非线性霍尔效应的启发，我们利用量子动力学方程研究了光电流。我们恢复了Sipe等人发现的移位电流和注入电流，以及Inti Sodemann和Liang Fu提出的Berry曲率偶极子（BCD）诱导的非线性霍尔电流。特别地，我们进一步提出除了Berry曲率和BCD外，3-形式张量也可以诱导光电流。这项工作将补充现有的光电流机制。与位移矢量诱导的位移电流不同，所有由Berry曲率的梯度/旋度和高阶张量诱导的光电流都需要圆偏振光和拓扑非平凡的能带结构，即非零Berry曲率。
英文摘要：
Motivated by the nonlinear Hall effect observed in topological semimetals, we studied the photocurrent by the quantum kinetic equation. We recovered the shift current and injection current discovered by Sipe et al., and the nonlinear Hall current induced by Berry curvature dipole (BCD) proposed by Inti Sodemann and Liang Fu. Especially, we further proposed that 3-form tensor can also induce photocurrent, in addition to the Berry curvature and BCD. This work will supplement the existing mechanisms for photocurrent. In contrast to the shift current induced by shift vector, all photocurrents induced by gradient/curl of Berry curvature, and high rank tensor require circularly polarized light and topologically non-trivial band structure, viz. non-vanishing Berry curvature.
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