All-Electric Semiconductor Spin Valve

提出了一种实验和理论研究相结合的方案，以开发一种具有大(~30)开/关电导比的全电动横向自旋阀。该装置将由砷化镓制成，不会使用任何铁磁电极或外部磁场来反转电子自旋。它由两个串联的量子点接触组成，中间有一条一维的短传导通道，在工作温度下，该通道的长度小于砷化镓的自旋相干长度。每个量子点接触充当全电动自旋偏振器或探测器，可以提供或过滤几乎完全自旋极化的电流。模型器件的非平衡格林S函数模拟表明，用现代光刻技术可以实现的基于长度为数十纳米的砷化镓量子点接触的自旋阀器件，可以产生足够大的自旋分裂，使得在常温下以大的开关电导进行可行的操作。智能价值纯电子手段产生、操纵和检测自旋极化电流是半导体自旋电子学中具有挑战性的目标。到目前为止，所研究的自旋阀使用嵌入到设备体系结构中的铁磁电极或材料来进行自旋极化和检测，并使用外部磁场来反转自旋。最近，我们证明了由半导体砷化铟制成的量子点接触可以通过纯电学手段产生强烈的自旋极化电流，当其限制势被栅极偏置电压高度不对称时。我们将在这个项目中开发的基于砷化镓量子点接触的自旋阀在两个方面都是独一无二的。首先，全电量子点接触将被用作自旋偏振器和探测器。第二，使用一维传输通道，它提供了比迄今使用的二维通道更多的优点。最后，由于在室温下砷化镓的自旋相干长度比砷化铟的自旋相干长度长(几十微米)，因此在常温下操作砷化镓自旋阀是可行的。如果成功，这个项目将是开创性的。更广泛的影响该项目的成功有望刺激全电动、超高速、高能效的自旋阀设备的发展，这些设备可用于高速数字信息处理，并最终用于基于自旋量子比特的固态量子计算。该项目如果成功，将是半导体自旋电子学的一个重大里程碑和突破。该项目的一个目标是开发第一个基于非平衡格林-S函数技术的模拟器来模拟纳米器件中的自旋输运，并通过NanHUB网站向科学界提供该模拟器。研究生和本科生都将参与这项研究工作。该项目将专门吸引泽维尔大学和辛辛那提大学的本科生从事尖端物理研究和传统本科课程和课程中无法获得的先进技术。

A concerted experimental and theoretical research program is proposed to develop an all-electric, lateral spin valve with a large (~ 30) On/Off conductance ratio. The device will be made from gallium arsenide and will not use any ferromagnetic electrodes or external magnetic field to flip the electron spin. It consists of two quantum point contacts in series separated by a short one-dimensional conduction channel of length smaller than the spin coherence length of gallium arsenide at the temperature of operation. Each quantum point contact acts as all-electric spin polarizer or detector and can provide or filter almost completely spin-polarized current. Non-equilibrium Green¡¦s function simulation of model devices indicate that spin valve devices based on gallium arsenide quantum point contacts on length scale of tens of nanometers, achievable with modern lithographic technology, can yield a large enough spin splitting to make feasible operation at ambient temperature with large On/Off conductance ratio.Intellectual meritThe creation, manipulation, and detection of spin-polarized currents by purely electrical means are challenging goals in semiconductor spintronics. Spin valves so far studied have used ferromagnetic electrodes or material embedded into device architecture for spin polarization and detection and an external magnetic field to flip the spin. Very recently, we have demonstrated that quantum point contact made from the semiconductor indium arsenide can be used to generate strongly spin polarized current by purely electrical means when its confining potential is made highly asymmetric by gate bias voltages. The spin valves based on gallium arsenide quantum point contacts we will develop in this project are unique in two respects. First, all-electric quantum point contacts will be used as spin polarizer and detector. Second, a one-dimensional transport channel is used that offers a number of advantages over two-dimensional channels used so far. Finally, because of the long (tens of micrometers) spin coherence length of gallium arsenide relative to that (tens of nanometers) of indium arsenide at room temperature, operation of the gallium arsenide spin valves at ambient temperature is feasible. If successful, this project will be ground-breaking. Broader ImpactsThe success of this project is expected to stimulate the development of all-electric, ultra high-speed, energy-efficient spin valve devices that can be used for high-speed digital information processing and eventually in solid-state quantum computation based on spin qubits. This project, if successful, will be a major milestone and a breakthrough in semiconductor spintronics. A goal of this project is to develop the first simulator based on non-equilibrium Green¡¦s function technique to model spin transport in nanoscale devices and make it available to the scientific community at large via the nanoHUB website. Both graduate and undergraduate students will participate in this research effort. This project will specifically engage undergraduate physics/engineering students of Xavier University and the University of Cincinnati to cutting edge physics research and advanced techniques not accessible in traditional undergraduate programs and courses.