Collaborative Research: Spin-electronic Dynamics in Three Terminal Couples Quantum Structures

Eric I. Altman，耶鲁大学“三终端耦合量子结构中的自旋电子动力学”这个项目的重点是探索使能技术，允许自旋自由度被用作量子通信和计算的控制机制。主要研究人员将制造和研究耦合量子点（QD）系统，该系统由紧密间隔的III-V半导体，砷化镓（GaAs）量子点组成，由分离电极控制。该系统将被设计成将自旋电荷传输到量子点中，并通过交换相互作用将它们耦合到相邻的点中。这样的系统是构建量子逻辑门的第一步，因为一个点的自旋通过交换库仑阻塞效应影响了其他点的电子电荷输运。自旋态和量子点之间的耦合程度也可以通过外加磁场和/或电场来控制。磁触点将作为自旋源，为载流子提供特定的自旋方向。这些载流子通过特定点的隧穿将取决于点中可用的自旋态。这提供了一种方便和实用的方法来确定特定点的自旋方向，从而确定该点在一定时间间隔后的自旋变化。在操纵和控制每个点的自旋态的背景下研究自旋动力学，以及在耦合量子点中共同研究自旋动力学，为制造量子晶体管和量子计算和通信器件的逻辑门提供了基础技术。耦合点系统的成功制造需要在宾厄姆顿州立大学采用最先进的合成方法。纳米尺度的电极结构的制造将在金属薄膜上使用光刻技术。在纳米尺度上制备半导体量子点，如砷化镓，将采用各种合成、加工和组装策略。还将开发生产GaAs:Mn纳米颗粒的方法；锰（Mn）掺杂可以提高量子点的自旋态工作温度。这些半导体纳米颗粒将在耶鲁大学和宾厄姆顿大学使用光谱和微观技术进行表征。利用光刻技术制备高度单分散的III-V型半导体纳米粒子，在两个金属电极之间形成数百纳米宽的窄间隙，研究相邻量子点之间的自旋电荷交换相互作用。详细的隧道特性作为温度和偏置的函数的研究将在宾厄姆顿的磁性低温恒温器中进行。在耶鲁大学，扫描隧道显微镜将用于表征纳米颗粒的大小、形态和电子特性以及它们在电极之间的位置。磁红外光谱将用于自组装半导体纳米粒子阵列，以检测量子点之间的自旋交换耦合。更广泛的影响：本研究将对基于自旋自由度的新型功能器件的未来技术产生重大影响，特别是为利用所开发的技术开发三端自旋场效应晶体管提供帮助。这些活动将使参与的研究生学习和准备自己成为开发下一代通信和计算设备的未来技术人员。将纳米结构和新型计算技术整合到课程中，将为相关学生提供更好的职业培训的跨学科经验。

Eric I. Altman, Yale University"Spin-electronic Dynamics in Three Terminal Coupled Quantum Structures"This project focuses on exploring enabling technologies to allow the spin degree of freedom to be used as the controlling mechanism for quantum communication and computing. The principal investigators will fabricate and study coupled quantum-dot (QD) systems consisting of closely spaced III-V semiconductor, gallium arsenide (GaAs) quantum dots controlled by separated electrodes. The systems will be designed to transmit spin charges into QDs and to couple them in the neighboring dots by exchange interaction. Such a system is the first step toward building quantum logic gates, because the spin of one dot affects the electronic charge transport in the other dots by the exchange coulomb blockage effect. The spin states and the degree of coupling between the quantum dots can also be controlled by applied magnetic and/or electric fields. Magnetic contacts will serve as spin sources to provide carriers with particular spin orientation. The tunneling of these carriers through a particular dot will depend on the available spin state in the dot. This provides a convenient and practical way of determining the spin orientation of a particular dot and thus the variation of the spin in this dot after a certain time interval. Studying the spin dynamics in the context of manipulating and controlling individual spin states in each dot, and collectively in coupled quantum dots provides basic technology for fabricating quantum transistors and logic gates for quantum computing and communication devices. Successful fabrication of coupled dot systems requires employing state of the art synthetic methods at SUNY Binghamton. The fabrication of electrode structures at nanometer scales will use lithography on metallic thin films. The preparation of semiconductor quantum dots, such as GaAs, in the nanometer scales will utilize various synthetic, processing and assembling strategies. Methods will also be developed to produce GaAs:Mn nanoparticles; the manganese (Mn) doping can enhance spin state operating temperature in quantum dots. These semiconductor nanoparticles will be characterized using spectroscopic and microscopic techniques at both Yale and Binghamton. The spin charge exchange interaction between neighboring QDs will be studied by producing highly monodispersed III-V semiconductor nanoparticles self-assembled in a narrow gap about hundreds of nanometers wide between two metallic electrodes made by lithography. The study of detailed tunneling characteristics as a function of temperature and bias will be carried out in a magnetic cryostat at Binghamton. At Yale, scanning tunneling microscopy will be used to characterize the size, morphology, and electronic properties of the nanoparticles and their positioning between the electrodes. Magneto-infrared spectroscopy will be carried out on self-assembled semiconductor nano-particle arrays to examine spin exchange coupling between QDs. Broader Impact: This research will strongly impact future technologies in new functional devices based on spin degree of freedom, particularly providing assistance to the development of three-terminal spin field-effect-transistors using the developed techniques. These activities will allow the graduate students involved to learn and prepare themselves to become future technologists for developing next generation communication and computing devices. The integration of the nanostructure and novel computing technology into the curricula will provide interdisciplinary experiences for better career training for the students involved.