Visualization of bulk and edge photocurrent flow in anisotropic Weyl semimetals
Visualization of bulk and edge photocurrent flow in anisotropic Weyl semimetals
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DOI：
10.1038/s41567-022-01898-0
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发表时间：
2022-03
期刊：
影响因子：
19.6
通讯作者：
Yu-Xuan Wang;Xin-Yue Zhang;Chunhua Li;Xiaohan Yao;Ruihuan Duan;Thomas Graham;Zheng Liu;F. Tafti;D. Broido;Ying Ran;B. Zhou
中科院分区：
文献类型：
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作者：
Yu-Xuan Wang;Xin-Yue Zhang;Chunhua Li;Xiaohan Yao;Ruihuan Duan;Thomas Graham;Zheng Liu;F. Tafti;D. Broido;Ying Ran;B. Zhou
在其本体中将光整流成电流的材料是光电应用所期望的。在破坏反转对称性的外尔半金属中，由于外尔节点附近增强的非线性光学过程，可能会产生体光电流。然而，这些材料的光响应通常通过扫描光电流显微镜来研究，该显微镜将光电流产生和收集的效果进行卷积。在这里，我们直接使用高灵敏度的量子磁学与氮空位中心自旋的II型外尔半金属WTe 2和TaIrTe 4内的光电流流动的图像。我们阐明了散装光电流产生的机制，我们称之为各向异性的光热电效应，其中不平等的热功率沿着不同的晶轴驱动器周围的光激发复杂的光电流循环。使用重叠扫描光电流显微镜和磁成像在内部和边缘的样品，我们可视化的各向异性光电效应如何刺激远程光电流收集在我们的WTe 2和TaIrTe 4设备通过肖克利-拉莫机制。我们的研究结果突出了一个广泛相关的电流源，并将激发光电探测器，利用体材料与热电各向异性。
Materials that rectify light into current in their bulk are desired for optoelectronic applications. In Weyl semimetals that break inversion symmetry, bulk photocurrents may arise due to nonlinear optical processes that are enhanced near the Weyl nodes. However, the photoresponse of these materials is commonly studied by scanning photocurrent microscopy, which convolves the effects of photocurrent generation and collection. Here we directly image the photocurrent flow inside the type-II Weyl semimetals WTe2and TaIrTe4using high-sensitivity quantum magnetometry with nitrogen-vacancy centre spins. We elucidate a mechanism for bulk photocurrent generation, which we call the anisotropic photothermoelectric effect, where unequal thermopowers along different crystal axes drive intricate circulations of photocurrent around the photoexcitation. Using overlapping scanning photocurrent microscopy and magnetic imaging at the interior and edges of the sample, we visualize how the anisotropic photothermoelectric effect stimulates the long-range photocurrent collected in our WTe2and TaIrTe4devices through the Shockley–Ramo mechanism. Our results highlight a widely relevant source of current flow and will inspire photodetectors that utilize bulk materials with thermoelectric anisotropy.