Controllable spin and charge transport in two-dimensional monochalcogenide semiconductors for spintronic devices

除了它们的电荷，电子还有一个固有的角动量，称为自旋，它与磁矩耦合。极化系综中电子自旋取向的操纵为新的逻辑器件和电路提供了基础，这些器件和电路具有当今基于电荷的设计的潜在优势。人们普遍认为，当自旋编码逻辑态时，具有最长自旋寿命的半导体材料是最适合用于注入和检测接触之间的传输通道的选择。然而，一旦逻辑运算完成，剩余的自旋可能并将干扰未来的运算。如果一种器件能够被设计成具有可控的自旋寿命，使得注入的自旋在逻辑操作中的传输过程中不会松弛，但在完成时通过诱导的快速平衡机制从通道中消失，那么它将比当前的自旋逻辑技术具有显著的优势。本研究的创新之处在于利用了具有各向异性自旋弛豫特性的半导体材料。拟议活动的影响是基于自旋的半导体器件和电路的潜力，以绕过基于电荷的电子的基本限制。此外，研究生将接受涉及半导体器件设计、加工、测量、磁学、低温技术的跨学科研究培训；推广活动将通过开发这项研究的科学内容演示来扩大中小学生、家长和普通公众对二维半导体的理解。自旋在注入时与量子化轴平行或反平行。逻辑运算完成后，自旋转移到器件的其他部分，静电门上的时钟电压脉冲产生一个电场，该电场感应出Bychkov-Rashba有效磁场。这个磁场与自旋轴不共线，从而使自旋相干地旋转到一个正交轴上，在这个轴上，强弛豫消除了它们的极化。然后重置逻辑环境。通过理论对称性分析，确定了几种基于石墨烯类蜂窝晶格的二维材料具有必要的各向异性自旋轨道性质。最有希望的候选材料体系是III族金属-单醇化合物单分子膜，称为III-VI-烯(‘3-6-烯’)。在这些反转不对称材料(如GaS、InS等)中，自旋轨道感生的波矢量相关的Dresselhaus有效磁场垂直于平面，使自旋上下自然本征态，通过动量散射的进动退位而不受Dyakonov-Perel弛豫的影响。为了控制自旋寿命，可以使用总是在平面内取向的静电门控产生的Bychkov-Rashba场来旋转自旋向平面，从而使进动消相导致有效的退极化。这项提议致力于开发三-六烯(具体地说，剥离的Gase)的独特性质，它将基于对称性的对这些材料中基本电子结构的理论理解与实验计划紧密结合起来，以证明预测的自旋和电荷传输装置中的各向异性驰豫效应。重点是了解复杂电子结构的实验结果，并为工程应用开发一种在自旋使能电路中实现三-六烯独特性质的方案。

In addition to their charge, electrons have an intrinsic angular momentum, called 'spin', that is coupled to a magnetic moment. Manipulation of electron spin orientation in polarized ensembles provides a basis for new logic devices and circuits with potential advantages over present-day charge-based designs. It is widely believed that whenever spin encodes logic state, semiconductor materials with the longest spin lifetime are the most suitable choice for transport channels between injection and detection contacts. However, once a logic operation is completed, residual spins can and will interfere with future operations. If a device can be designed with a controllable spin lifetime such that injected spins do not relax during transport in a logic operation but upon completion vanish from the channel by an induced fast equilibration mechanism, it will have a significant advantage over the current spin logic technology. The innovation of the proposed research lies in making use of semiconductor materials having anisotropic spin relaxation. The impact of the proposed activity is in the potential of spin-based semiconductor devices and circuits to circumvent the fundamental limitations of charge-based electronics. In addition, graduate students will be trained in interdisciplinary research involving semiconductor device design, processing, measurement, magnetism, low-temperature techniques; and outreach activities will extend to broaden understanding of 2-dimensional semiconductors to elementary and high-school students, parents, and the general public by developing demonstrations of the scientific contents of this research.Spins are initially aligned parallel or antiparallel to the quantization axis at injection. After the completion of a logic operation, spin transpors to other parts of the device and a clocked voltage pulse on an electrostatic gate generates an electric field that induces a Bychkov-Rashba effective magnetic field. This magnetic field is non-colinear to the spin axis and thus coherently rotates the spins onto an orthogonal axis where strong relaxation eliminates their polarization. The logic environment is then reset. Through theoretical symmetry analysis it has been determined, several two-dimensional materials that are based on graphene-like honeycomb lattice have the requisite anisotropic spin-orbit properties. The most promising candidate material system is the group-III metal-monochalcogenide monolayers, called III-VI-ene ('three-six-ene'). In these inversion asymmetric materials (such as GaSe, InS, etc), the spin-orbit-induced wave-vector- dependent Dresselhaus effective magnetic field is oriented perpendicular to the plane, making spin up/down the natural eigenstates, immune to Dyakonov-Perel relaxation via precessional dephasing upon momentum scattering. To control spin lifetime, a Bychkov-Rashba field resulting from electrostatic gating that is always oriented in-plane can be used to rotate spins toward the plane so that precessional dephasing leads to efficient depolarization. This proposal deals to exploit the unique properties of three-six-enes (specifically, exfoliated GaSe) that intimately combines the symmetry-based theoretical understanding of the fundamental electronic structure in these materials with an experimental plan to demonstrate the predicted anisotropic relaxation effects in spin- and charge-transport devices. The focus is on understanding the experimental consequences of complex electronic structure and develop a scheme for implementation of the unique properties of three-six-enes in spin-enabled circuits for engineering applications.