EAGER: Designing a molecular scale spin-switch

智力优势：随着硅基计算设备接近其小型化的基本极限，量子控制的分子尺度电子学有望在电子设备的最终小型化中应对量子力学施加的物理挑战。研究如何控制分子体系中的电子输运？S提供的自旋自由度将为新兴的分子尺度电子学领域增加一个新的维度。这有几个好处。首先，在低原子序数(Z)的碳基分子系统中，弱的自旋-轨道和超精细相互作用导致它们具有比传统金属和半导体更长的自旋相干长度。其次，低成本的生产、化学灵活性和自组装方法为分子作为可行的自旋传输互连提供了巨大的优势。第三，由于自旋是我们可以存储信息的最终逻辑位，操纵分子电路中的自旋以获得所需的设备行为将有利于计算，因为信息存储和处理都可以集成在单个芯片中。拟议项目的目标是探索一种分子尺度自旋开关的创新体系结构，并确定该设备的基本分子构件。我们的目标是从根本上理解自旋调制的电子传输，这将构成功能器件设计的基础。镍、钴等过渡金属将被用作自旋偏振器和分析器(过滤器)，低Z原子的分子络合物将被用作磁性电极之间的桥梁，有机金属分子和碳纳米管结构将被用于可能的互联。选择有机金属分子络合物作为互连的原因在于，它可以很容易地通过栅场来调节分子中金属键的电子自旋态，从而提供对自旋极化电子电流的额外电子控制--这是自旋开关的效果先决条件。碳纳米管(CNT)将是另一个自旋输运的候选材料，因为碳纳米管中的自旋反转散射长度被报道要高得多。第一原理密度泛函理论和无参数单粒子格林-S函数方法将为理解自旋极化电子在该器件中的受控输运提供预测能力。我们将系统地研究界面和接触点的电子结构和磁配置的作用，以优化器件设计中磁阻的最大调制。拟议的可行性研究将指导未来成功实现这种装置的理论和实验努力。广泛影响：该项目将产生几个更广泛的影响：a)确定一种新的分子自旋开关结构，用于从超小型磁传感器到基于自旋逻辑的分子计算的多功能应用，远远超出2020年的技术路线图；b)对该装置中的自旋调制电子传输有基本的了解，这将有助于指导未来旨在实现此类装置的理论和实验工作；c)促进多学科的研究和合作；D)培训研究生在第一原理建模方面获得第一手经验；e)提供将教育与研究相结合的途径；f)广泛传播项目成果(研究和教育)，并为社会带来长期的高回报利益。由于拟议的项目有望冒险进入先进分子自旋电子学的一个新兴研究想法，它满足了渴望拨款的重要标准。

Intellectual merit:With the silicon based computing devices approaching its fundamental limit of miniaturization, quantum controlled molecular scale electronics bears the only possible hope to meet the physical challenges imposed by quantum mechanics in the ultimate miniaturization of electronic devices. Learning how to control the electron transport in molecular systems offered by electron?s spin degrees of freedom would add a new dimension to the emerging field of molecular-scale electronics. There are several advantages. First, the weak spin-orbit and hyperfine interaction in carbon based molecular systems with atoms having low atomic numbers (Z) lead them to have a longer spin coherence length than that in conventional metals and semiconductors. Second, the low cost production, chemical flexibility, and self-assembly approach offer tremendous advantages for molecules as a viable interconnects for spin transport. Third, since spin is the ultimate logic bit where we can store information, manipulating the spin in a molecular circuit for a desired device behavior would be beneficial for computing as both information storing and processing can be integrated within a single chip. The objectives of the proposed project are to explore an innovative architecture for a molecular scale spin switch and identify the basic molecular building blocks for this device. The goal is in fundamental understanding of the spin modulated electron transport which would form the basis for functional device design. Transition metals like Ni and Co will be used as spin polarizer and analyzer (filter), molecular complex with low-Z atoms will be used as a bridge between the magnetic electrodes, and organo-metallic molecule and carbon nanotube structures for possible interconnect. The reason behind the choice of organo-metallic molecular complex as the interconnect lies in the fact that it can easily tune the electronic spin state of the metal link in the molecule by gate field providing additional electrical control of spin polarized electronic current-an effect prerequisite for a spin switch. Carbon nanotube (CNT) will be another candidate for spin transport as spin-flip scattering length in CNT has been reported to be much higher. First principles density functional theory together with a parameter free single particle Green?s function approach will be used to provide predictive capability to understand the controlled transport of spin polarized electrons in this device. The role of electronic structure and magnetic configurations at the interface and at the contact points will be systematically studied to optimize maximum modulation in magneto-resistance for device design. The proposed feasibility study will guide the future theoretical and experimental endeavors towards a successful realization of such a device.Broader Impact:This project will yield several broader impacts: a) Identify a novel architecture for a molecular spin-switch for multi-functional applications ranging from ultra-small magnetic sensors to spin logic based molecular computing that goes far beyond the technology roadmap for the year 2020; b) Develop fundamental understanding of spin modulated electron transport in this device, which will be helpful in guiding the future theoretical and experimental efforts aimed at realizing such devices; c) Stimulate multi-disciplinary research and collaborations; d) Train graduate students in getting first-hand experience in first-principles modeling; e) Provide avenues to integrate education with research; f) broad dissemination of project results (both research and education) and long-term high-reward benefits to society. Since the proposed project is expected to venture into an emerging research idea in advanced molecular spintronics, it satisfies the important criteria for EAGER grant.