Optical Spin Orientation and Transport in Layered Mono- and Di-Chalcogenide Semiconductors

非技术描述：计算逻辑的电子设备传统上是基于电子的电荷，但由于热量和尺寸的限制，扩展这项技术变得越来越困难，需要新的物理系统来改进逻辑设备。解决这个问题的一种可能性是利用电子的“自旋”，而不是利用它的电荷，后者需要的能量更少，产生的热量也更少。将这种方法转化为新兴的纳米材料，很可能揭示出以尽可能小的长度尺度运行的小型化、低功率自旋电子产品的方法。这项研究的重点是了解如何在纳米材料系统中定向和传输自旋和自旋类似物，以利用单层晶体原子尺度极限的优势。这些努力可能会产生广泛的影响，使层状原子薄层材料的优势可用于基于自旋的设备，从而有助于顺利采用这些令人兴奋的材料，用于纳米技术，超越现有众所周知的块状系统的功能。所支持的活动有助于指导精通光学、量子材料和纳米科学的下一代科学工作者。这项研究融入了对课程的教学改进，促进了不同学生的科学兴趣和热情。技术描述：利用光来定向自旋和诱导自旋电流的能力一直是研究块状材料中自旋电子学的关键工具。通过研究几类已知支持自旋相关现象的非中心对称晶体，这项研究解释了三维自旋电子学中使用的光学方法的优势，以揭示低维的新效应。除了以前利用光来控制自旋的工作之外，这个项目还研究了几个悬而未决的问题，包括(I)光激发的自旋输运是如何在低维界面上演化的，以及(Ii)二维材料中常见的非中心对称晶体能否增强控制光诱导信息的能力。为了解决这些问题，这项研究使用两种不同但互补的方法来探索自旋取向和输运现象。第一个主题利用层状范德华材料独特的原子尺度、界面和异质结构能力来理解自旋谷流。本活动旨在测量光电子器件中谷霍尔效应的界面效应。这项研究的第二个主题方向是探索对几层单硫化物中有利的自旋性质的预测，这表明这种材料类别适合于传统的光学自旋取向方法。本课题旨在测量硒化铟的光致自旋动力学，并控制电子和核自旋系综之间的自旋极化转移。为实现这些目标而开展的研究促进了对自旋输运和光学取向的理解，并扩展了可用于在二维材料中操纵自旋的工具，从而为高度定制的微型化光电子创造了机会。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical description: Electronic devices for computing logic are traditionally based on the charge of electrons, but as scaling this technology becomes increasingly difficult due to heat and size constraints, new physical systems are necessary for improving logic devices. One possibility to tackle this problem is to utilize an electron's "spin" rather than its charge, which requires less energy and produces less heat. Translating this approach to emerging nano-scale materials is likely to reveal approaches for miniaturized low-power spin-based electronics functioning at the smallest length scales possible. This research focuses on understanding how to orient and transport spin and spin-analogs in nanomaterial systems that harness the advantages of the ultimate atomic-scale limit of single layered crystals. These efforts could have broad impact by making the advantages of layered atomically-thin materials available to spin-based devices, thereby helping to smooth adoption of these exciting materials for nano-scale technologies that surpass the functionality of existing well-understood bulk systems. The supported activities facilitate mentoring of the next generation scientific workforce fluent with the intersection of optics, quantum materials, and nano-science. This research integrates into pedagogical improvements to curriculum that promote scientific interest and enthusiasm for diverse students. Technical description: The ability to use light to orient spins and induce spin currents has been a key tool in the study of spintronics in bulk materials. By studying several classes of non-centrosymmetric crystals that are already known to support spin-related phenomena, this research translates the advantages of optical methods used in three-dimensional spintronics to reveal novel effects in low dimensions. Going beyond previous work exploiting light to control spin, this project investigates several unanswered questions, including (i) how optically-excited spin transport evolves over low-dimensional interfaces, and (ii) can the non-centrosymmetric crystals common in two-dimensional materials enhance the ability to control optically-induced information. To address these questions, this research explores spin orientation and transport phenomena using two distinct, but complementary, approaches. The first theme exploits the unique atomic-scale interfacial and heterostructure capabilities of layered van der Waals materials to understand spin-valley currents. This activity aims to measure interface effects of the valley Hall effect in opto-electronic devices. The second thematic direction of this research explores predictions of favorable spin properties in few-layer mono-chalcogenides that suggest suitability of this material class for traditional optical spin orientation methods. This theme aims to measure optically-induced spin dynamics in indium selenide and control transfer of spin polarization between electron and nuclear spin ensembles. Research carried out toward these goals advances understanding of spin transport and optical orientation and expands the tools available for spin manipulation in two-dimensional materials, thereby creating opportunities for highly tailored miniaturized opto-electronics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.