标题： 低温扫描光电流光谱研究材料对结构化光场的响应 显示英文标题

标题： Cryogenic scanning photocurrent spectroscopy for materials responses to structured optical fields

摘要： 圆二色光谱被证明能够提供关于量子材料中不同自由度相互作用的重要见解，然而，对于量子材料对具有有限自旋和轨道角动量的结构化光学场（如光）的光电子响应的光谱研究尚未得到广泛探索，尤其是在低温条件下。 在此，我们展示了新型仪器的设计与应用，该仪器集成了扫描光谱光电流测量与可控自旋和轨道角动量的结构光。对于波长在500纳米到700纳米之间的结构光子，此仪器能够在高达$\pm$ 14特斯拉的磁场下，从300开尔文到3开尔文的温度范围内，对二维材料或薄晶体进行空间分辨光电流测量，并且可以使用自旋角动量 $\pm \hbar$ 或轨道角动量 $\pm \ell \hbar$ （其中 $\ell$=1,2,3... 是拓扑荷），覆盖一个 (35 $\times$ 25) $\mu m^2$ 区域，空间分辨率为~ 1 $\mu m$。 这种仪器的能力可以通过单层 2H-$MoS_2$场效应晶体管的磁光 photocurrent 光谱测量来加以说明，这些测量不仅揭示了激子光谱，还展示了随着 |$\ell $| 增加，光电流单调增加，以及由于磁场下能谷间暗激子形成增强而产生的激子 Zeeman 分裂和增强的地磁场因子。 因此，这些研究证明了扫描 photocurrent 光谱技术在研究新型量子材料和工程量子设备中的激子物理、光学选择规则以及对结构光的光电子响应方面的多功能性。 显示英文摘要

摘要： Circular dichroism spectroscopy is known to provide important insights into the interplay of different degrees of freedom in quantum materials, and yet spectroscopic study of the optoelectronic responses of quantum materials to structured optical fields, such as light with finite spin and orbital angular momentum, has not yet been widely explored, particularly at cryogenic temperature. Here we demonstrate the design and application of a novel instrument that integrates scanning spectroscopic photocurrent measurements with structured light of controlled spin and orbital angular momentum. For structured photons with wavelengths between 500 nm to 700 nm, this instrument can perform spatially resolved photocurrent measurements of two-dimensional materials or thin crystals under magnetic fields up to $\pm$ 14 Tesla, at temperatures from 300 K down to 3 K, with either spin angular momentum $\pm \hbar$ ororbital angular momentum $\pm \ell \hbar$ (where $\ell$=1,2,3... is the topological charge), and over a (35 $\times$ 25) $\mu m^2$ area with ~ 1 $\mu m$ spatial resolution. These capabilities of the instrument are exemplified by magneto-photocurrent spectroscopic measurements of monolayer 2H-$MoS_2$ field-effect transistors, which not only reveal the excitonic spectra but also demonstrate monotonically increasing photocurrents with increasing |$\ell $| as well as excitonic Zeeman splitting and an enhanced Land\'e g-factor due to the enhanced formation of intervalley dark excitons under magnetic field. These studies thus demonstrate the versatility of the scanning photocurrent spectrometry for investigating excitonic physics, optical selection rules, and optoelectronic responses of novel quantum materials and engineered quantum devices to structured light.