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

除了它们的电荷，电子还有一个内在的角动量，称为“自旋”，它与磁矩耦合。 在极化系综中操纵电子自旋取向为新的逻辑器件和电路提供了基础，这些逻辑器件和电路比当今基于电荷的设计具有潜在的优势。 人们普遍认为，每当自旋编码逻辑状态时，具有最长自旋寿命的半导体材料是注入和检测接触之间的传输通道的最合适的选择。 然而，一旦逻辑操作完成，剩余的自旋可以并且将干扰未来的操作。 如果可以设计具有可控自旋寿命的器件，使得注入的自旋在逻辑操作中的传输期间不松弛，而是在完成时通过诱导的快速平衡机制从沟道消失，则其将具有优于当前自旋逻辑技术的显著优势。 本研究的创新之处在于利用了具有各向异性自旋弛豫的半导体材料。拟议活动的影响在于基于自旋的半导体器件和电路的潜力，以规避基于电荷的电子学的基本限制。 此外，研究生将接受跨学科研究的培训，涉及半导体器件设计、加工、测量、磁学、低温技术;和推广活动将扩大对二维半导体的理解，以小学和高中学生，家长，通过开发这项研究的科学内容的演示，向公众和公众展示。旋转最初平行或反平行于注入时的量化轴。 在完成逻辑运算之后，自旋转移到器件的其他部分，并且静电门上的时钟电压脉冲产生感应Bychkov-Rashba有效磁场的电场。 该磁场与自旋轴不共线，因此相干地将自旋旋转到正交轴上，其中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，已经确定，基于石墨烯类蜂窝晶格的几种二维材料具有必要的各向异性自旋轨道性质。最有前途的候选材料系统是III族金属-单硫属化物单层，称为III-VI-ene（“三六烯”）。在这些反转非对称材料（如GaSe、InS等）中，自旋-轨道诱导的波矢相关的Dresselhaus有效磁场垂直于平面取向，使得自旋上/下的自然本征态，通过动量散射时的进动退相而不受Dyakonov-Perel弛豫的影响。为了控制自旋寿命，由静电门控产生的总是在平面内取向的Bychkov-Rashba场可以用于使自旋朝向平面旋转，使得进动退相导致有效的去极化。 该提案涉及利用三-六烯（具体而言，剥离的GaSe）的独特性质，将这些材料中基本电子结构的基于量子力学的理论理解与实验计划紧密结合起来，以证明自旋和电荷传输器件中预测的各向异性弛豫效应。 重点是了解复杂的电子结构的实验结果，并制定一个计划，用于实施的独特性质的三-六-烯自旋使能电路的工程应用。

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.