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

为了充分发挥自旋器件的潜力，必须找到通过纯电学手段注入、操纵和检测电子自旋的方法。最近，首席研究员（PI）成功地证明了横向自旋轨道耦合（LSOC）可以通过纯电手段产生强自旋极化电流；也就是说，在没有任何外加磁场的情况下。PI建议将这些研究扩展到自旋阀结构，该结构由量子点或导线通过不对称偏置量子点接触（QPCs）耦合到源极和漏极。由于两个qpc的栅极上存在不对称偏置，当它们的自旋滤波与通过有源通道的库仑阻塞输运相结合时，将导致通过自旋阀的自旋阻塞输运。当操作接近阈值时，所有的电自旋阀也可以用于研究新的多体效应，如电控制自发自旋极化、Wigner结晶和纳米级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：计划与瑞典林雪平大学合作开展研究，首次对LSOC存在下全电动自旋阀的库仑/自旋阻塞和维格纳结晶机制进行理论研究。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基于多粒子Fock空间和稳态速率方程建立一个理论框架，并计算这些自旋阀的电导。理论工作将补充辛辛那提大学最近的实验工作，以创造所有电动自旋阀和其他最近关于量子点中单自旋的量子操纵的报告，这些报告依赖于微妙的自旋相关效应，导致有趣的非线性输运现象，如负微分区（NDR），多重NDR和双稳定性。更广泛的影响：在LSOC存在的情况下，对所有电动自旋阀中的库仑和自旋阻塞以及Wigner结晶的全面理解将是自旋电子学领域的一个重要里程碑。对强相关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取得未来的进展。如果成功，该项目很可能在理论上产生第一个模拟器，包括库仑和自旋封锁的影响，并模拟在LSOC存在下纳米级器件中的自旋输运。所开发的软件将有助于研究用于自旋传感器、自旋滤波器、多电平逻辑电路和数据存储应用的所有电动自旋阀的异质结构参数的设计和制造。该项目旨在促进辛辛那提大学电子与计算系统学院与瑞典林雪平物理、化学和生物系之间的新合作。这项工作将成为辛辛那提大学和林雪平大学之间长期合作的先驱，通过研究交流计划吸引两国的本科生和研究生物理/工程专业学生，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.