CNIC: U.S.-Swedish Engineering Research on Spin Blockaded Transport and Onset of Wigner Crystallization in All Electric Spin Valves

为了实现基于自旋的器件的全部潜力，必须找到通过纯电子手段注入、操纵和检测电子自旋的方法。最近，首席研究人员(PI)成功地证明了侧向自旋轨道耦合(LSOC)可以通过纯电学手段，即在没有任何外加磁场的情况下，产生强烈的自旋极化电流。PI建议将这些研究扩展到由量子点或线组成的自旋阀结构，这些量子点或线通过非对称偏置的量子点接触(QPC)耦合到源和漏。由于两个QPC的栅极具有不对称的偏置，当它们的自旋过滤与库仑阻塞的通过主动通道的输运相结合时，应该会导致自旋受阻的输运通过自旋阀。当接近阈值工作时，所有的电自旋阀也可以用来研究新的多体效应，如电控自发自旋极化、Wigner结晶和纳米器件中自旋晶格的形成，这些都是自旋电子学研究的新兴领域。智力优势：拟议的计划访问将与瑞典合作伙伴在林科平大学启动研究，以提供在LSOC存在下全电动自旋阀中库仑/自旋阻塞和Wigner结晶操作的第一个理论研究。由于这些多体效应不能用单粒子哈密顿方法建模，合作的技术方法将是发展一个基于多粒子Fock空间和稳态速率方程的理论框架，并计算这些自旋阀的电导。理论工作将是对辛辛那提大学最近创建所有电动自旋阀的实验工作的补充，以及其他最近关于量子点中单个自旋的量子操纵的报告，这些报告依赖于微妙的自旋关联效应，导致有趣的非线性输运现象，如负微分区(NDR)、多个NDR和双稳。更广泛的影响：彻底理解库仑和自旋阻塞，以及在LSOC存在的情况下所有电动自旋阀中的维格纳结晶将是自旋电子学领域的一个重要里程碑。对强关联系统中这些非线性效应的深入理解将有助于在涉及非平衡动力学的领域中取得未来的进展。如果成功，该项目很可能在理论上生产出第一个包含库仑和自旋阻塞效应的模拟器，并在LSOC存在的情况下模拟纳米设备中的自旋输运。开发的软件将有助于研究用于自旋传感器、自旋过滤器、多电平逻辑电路和数据存储应用的所有电动自旋阀的设计和制造的异质结构参数。所描述的项目旨在促进辛辛那提大学电子和计算系统学院与瑞典林科平的物理、化学和生物系之间的新合作。这一努力将成为辛辛那提大学和林科平大学之间长期合作的先导，通过一个研究交流计划，让两国的本科生和研究生物理/工程学学生参与进来，在此期间，学生将受益于具有互补专业知识的工程师和物理学家的指导。

To realize the full potential of spin-based devices, ways must be found to inject, manipulate, and detect the spin of the electron by purely electrical means. Recently, the Principal Investigator (PI) successfully demonstrated that lateral spin orbit coupling (LSOC) can be used to create a strongly spin-polarized current by purely electrical means; that is, in the absence of any applied magnetic field. The PI proposes to extend these studies to spin valve structures composed of a quantum dot or wire coupled to the source and drain via asymmetrically biased quantum point contacts (QPCs). With an asymmetric bias on the gates of the two QPCs, their spin filtering, when combined with Coulomb blockaded transport through the active channel, should lead to spin-blockaded transport through the spin valve. When operated close to threshold, all electrical spin valves could also be used to investigate new many-body effects, such as electrically controlled spontaneous spin polarization, Wigner crystallization and formation of spin lattices in nanoscale devices, which are burgeoning fields of spintronics research.Intellectual Merit:The proposed planning visit to initiate research with Swedish partners at the University of Linkoping to provide the first theoretical investigation of the Coulomb/Spin Blockades and Wigner Crystallization regimes of operation in all-electric spin valves in the presence of LSOC. Since these many-body effects cannot be modeled using a one-particle Hamiltonian approach, the cooperative technical approach will be to develop a theoretical framework based on a multi-particle Fock space and steady-state rate equations, and to calculate the conductance of these spin valves. Theoretical efforts will complement recent experimental efforts at the University of Cincinnati to create all electric spin valves and other recent reports on quantum manipulation of single spins in quantum dots which rely on subtle spin correlation effects leading to intriguing non-linear transport phenomena such as Negative Differential Region (NDR), multiple NDR, and bistability.Broader Impacts:A thorough understanding of the Coulomb and Spin Blockades, and Wigner crystallization in all electric spin valves in the presence of LSOC would be a major milestone in the field of spintronics. A deep understanding of these non-linear effects in strongly correlated systems will contribute to future advancement in fields where non-equilibrium dynamics are involved. If successful, this project is likely to theoretically produce the first simulator that includes the effects of Coulomb and Spin blockade and models spin transport in nanoscale devices in the presence of LSOC. The software developed will be useful to investigate heterostructure parameters for design and fabrication of all electric spin valves for applications in spin-based sensors, spin filters, multilevel logic circuits and data storage applications. The project described is intended to catalyze new collaboration between the School of Electronics and Computing Systems at the University of Cincinnati and the Department of Physics, Chemistry and Biology in Linkoping, Sweden. This effort will serve as a precursor for long-term collaboration between Cincinnati and Linkoping Universities to engage undergraduate and graduate physics/engineering students in both countries through a research exchange program during which the students would benefit from the guidance of engineers and physicists with complementary expertise.