级联圆光电流和非线性霍尔效应产生的四阶光电响应
Fourth-order Optoelectronic Response from Cascaded Circular Photogalvanic and Nonlinear Hall Effects
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中文总结 AI 辅助
研究揭示非中心对称二维材料中由圆光电流效应和贝里曲率偶极子相互联系产生的四阶光电响应，以单层$\Td$-WTe$_2$为原型，通过光学几何结构调节级联光电压，可实现相关探测及器件应用。
中文摘要 AI 辅助
非线性光学跃迁与拓扑能带结构之间的相互作用为控制光电流提供了一条途径。我们揭示了一种四阶光电响应，它出现在非中心对称二维材料中的圆光电流效应（CPGE）和贝里曲率偶极子（BCD）之间的相互联系中。以单层$\Td$-WTe$_2$为原型，我们预测圆偏振中红外光会产生稳定的直流注入电流，该电流会感应出内部电场，进而通过BCD驱动横向非线性霍尔响应。由此产生的级联光电压与光场的四次方$E_0^4$成正比。通过绘制完整的注入电流张量，我们表明这种级联电压可通过光学几何结构进行强烈调节：垂直入射驱动面内共振$\mathrm{Im}(\eta_{yxy})$，而斜入射（$\theta = 45^{\circ}$）则产生占主导地位的面外分量$\mathrm{Im}(\eta_{yyz})$，并将信号放大两个多数量级（${\sim}10^2~\mu$V）。虽然大量的线性德鲁德背景通常会屏蔽半金属中的非线性响应，但我们认为光泵浦的幅度调制允许锁定检测以干净地分离倍频级联响应。所提出的机制将中红外光转换为门可调横向信号，为探测量子几何结构以及实现拓扑光电探测器和倍频器提供了一条途径。
英文摘要
The interplay between nonlinear optical transitions and topological band structure offers a route to control photocurrents. We reveal a fourth-order optoelectronic response that emerges due to an interlink between the circular photogalvanic effect (CPGE) and the Berry curvature dipole (BCD) in noncentrosymmetric 2D materials. Using monolayer $\Td$-WTe$_2$ as a prototype, we predict that circularly polarized mid-infrared light produces a steady dc injection current that induces an internal electric field, which in turn drives a transverse nonlinear Hall response through BCD. The resulting cascaded photovoltage scales as the fourth power of the optical field $E_0^4$. By mapping the full injection current tensor, we show that this cascaded voltage is strongly tunable by the optical geometry: normal incidence drives an in-plane resonance $\mathrm{Im}(η_{yxy})$, whereas oblique illumination ($θ= 45^{\circ}$) recruits a dominant out-of-plane component $\mathrm{Im}(η_{yyz})$ and amplifies the signal by more than two orders of magnitude (${\sim}10^2~μ$V). While the massive linear Drude background typically screens nonlinear responses in semimetals, we argue that the amplitude modulation of the optical pump allows lock-in detection to cleanly isolate the frequency-doubled cascaded response. The proposed mechanism converts mid-infrared light into a gate-tunable transverse signal, providing a route for probing quantum geometry and realizing topological photodetectors and frequency doublers.
