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

非技术描述：用于计算逻辑的电子设备传统上是基于电子电荷的，但由于热量和尺寸限制，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是利用电子的“自旋”而不是它的电荷，这需要更少的能量和产生更少的热量。将这种方法应用到新兴的纳米级材料中，可能会揭示在尽可能小的长度尺度上运行的小型化低功率自旋电子器件的方法。本研究的重点是了解如何利用单层晶体的终极原子尺度限制的优势，在纳米材料系统中定向和传输自旋和自旋类似物。这些努力可能会产生广泛的影响，使层状原子薄材料的优势可用于基于旋转的设备，从而有助于将这些令人兴奋的材料顺利应用于纳米级技术，超越现有的良好理解的体系统的功能。支持的活动有助于指导下一代科学工作人员流利地掌握光学，量子材料和纳米科学的交叉。本研究整合了教学改进课程，以促进不同学生的科学兴趣和热情。技术描述：利用光定向自旋和诱导自旋电流的能力已经成为研究大块材料中自旋电子学的关键工具。通过研究几种已知支持自旋相关现象的非中心对称晶体，本研究将三维自旋电子学中使用的光学方法的优势转化为揭示低维的新效应。超越以往利用光来控制自旋的工作，该项目研究了几个悬而未决的问题，包括(i)光激发自旋输运如何在低维界面上演变，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，本研究使用两种不同但互补的方法探索自旋取向和输运现象。第一个主题是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电流。本活动旨在测量光电器件中谷霍尔效应的界面效应。本研究的第二个主题方向是探索对少数层单硫族化合物有利自旋特性的预测，这表明这类材料适合传统的光学自旋取向方法。本课题旨在测量硒化铟的光诱导自旋动力学，并控制电子和核自旋综间的自旋极化转移。朝着这些目标进行的研究促进了对自旋输运和光取向的理解，并扩展了二维材料中自旋操纵的工具，从而为高度定制的小型化光电子技术创造了机会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.