Collaborative Research: Molecular Spintronics with Single-Molecule Magnets

本提案的总体目标是探索单个分子的局部高自旋态与传导电子之间的相互作用，以开发用于局部磁场传感，超高密度信息存储和量子信息处理的分子电子器件。单分子磁体具有大的总自旋和强的本征各向异性。它们表现出一些独特的特性，如磁化的量子隧穿和贝里相位干涉。尽管在晶体形式下进行了广泛的研究，但它们的一些关键性质仍然难以捉摸。例如，目前尚不清楚磁化的量子隧穿如何影响通过这些分子的电子传导。理解这一特性对于任何电子设备的开发都是至关重要的。提出的研究计划通过结合化学合成与实验和理论物理来探测孤立的单分子磁体的量子特性来解决这些问题。这些分子将附着在纳米间隙的金属电极上，并通过电门控形成单电子晶体管。器件制造将利用光刻和电迁移技术。分子?通过静态和动态两方面的研究，揭示分子的激发态、不同配体的影响、近藤效应、自旋极化输运、berry相阻滞、磁化的量子振荡和退相干。本研究的重点是在实际设备上探索这些现象。特别是：(1)利用Berry相的强磁场可调性获得高灵敏度的局部磁场纳米传感器；（ii）开发高密度磁存储器中分子位的读写程序；（iii）在分子量子比特中演示量子逻辑门操作。该团队在单分子磁体和量子电子输运方面拥有丰富的经验。初步的结果已经证明了团队？我们有能力制造合适的设备，并测量库仑封锁区分离分子的IV特性。现有的设备可以在短的周转时间内有效地制造设备。该团队可用的设备包括低温，任意方向的高磁场，连续波和脉冲高频微波激励，以及超高速脉冲电压门控。知识优势：分子电子学正迅速成为应用科学与工程领域的一个独立研究领域。到目前为止，主要的努力是在碳基系统或各向同性分子上，这些分子含有一个小的净自旋。这一建议的重点是由于其大自旋和强轴向各向异性而具有本质磁性的分子。研究范围包括化学、物理、设备制造和开发，以及低温和高磁场下的基础研究。提出的研究将导致更好地理解孤立的单分子磁体的量子特性，以及如何在单电子晶体管设置中将磁性与电子输运结合起来。更广泛的影响：该提案将推进我们对单分子电子设备的了解。这些器件在超高密度集成和量子信息处理方面具有巨大的潜力，可能会带来新的革命性技术。几名研究生和本科生将在不断跨越这些学科界限的环境中接受无机化学与基础和应用物理之间界面的培训。

The broad goal of this proposal is to explore the interplay between localized high-spin states of an individual molecule and conduction electrons in order to develop molecular electronic devices for local magnetic field sensing, ultra-high-density information storage, and quantum information processing. Single-molecule magnets are characterized by a large total spin and a strong intrinsic anisotropy. They present some unique characteristics, such as quantum tunneling of the magnetization and Berry phase interference. Although extensively studied in crystalline form, some of their key properties remain elusive. For instance, it is unclear how quantum tunneling of the magnetization influences electronic conduction through these molecules. Understanding this property is crucial for any electronic device development. The proposed research program addresses these issues by combining chemical synthesis with experimental and theoretical physics to probe quantum properties of isolated single-molecule magnets. The molecules will be attached to nanometer-gapped metal electrodes and gated electrically to form a single-electron transistor. Device fabrication will make use of lithographic and electromigration techniques. The molecule?s electric conduction will be studied both statically and dynamically to reveal excited molecular states, the effect of different ligands, the Kondo effect, spin-polarized transport, the Berry-phase blockade, quantum oscillations of the magnetization, and decoherence,. The proposed study emphasizes exploring these phenomena toward practical devices. In particular: (i) to employ the intense magnetic field tunability of the Berry phase to obtain high-sensitivity local magnetic field nanosensors; (ii) to develop reading and writing procedures for molecular bits in high-density magnetic memories; and (iii) to demonstrate quantum logic gate operations in a molecular qubit. The team has extensive experience with single-molecule magnets and in quantum electronic transport. Preliminary results have demonstrated the team?s ability to fabricate suitable devices and to measure the IV characteristics of isolated molecules in the Coulomb blockade regime. Available facilities permit efficient device fabrication with a short turnover time. The facilities available to the team include low temperatures, high magnetic fields oriented in arbitrary directions, continuous-wave and pulsed high-frequency microwave excitations, and ultra-fast pulsed voltage gating.Intellectual Merit: Molecular electronics is rapidly becoming a separate research field within Applied Sciences and Engineering. The main effort so far has been on carbon-based systems or isotropic molecules containing a small net spin. This proposal focuses on molecules that are intrinsically magnetic due to their large spin and strong axial anisotropy. The research encompasses chemistry, physics, device fabrication and development, as well as fundamental studies at low temperatures and high magnetic fields. The proposed studies will lead to a better understanding of the quantum properties of isolated single-molecule magnets and how magnetism can be combined with electronic transport in a single-electron transistor setup.Broader Impact: The proposal will advance our knowledge of single molecule-based electronic devices. These devices have great potential for ultra-high density integration and quantum information processing, which may lead to new and revolutionary technologies. Several graduate and undergraduate students will be trained in the interface between inorganic chemistry and fundamental and applied physics within an environment that constantly crosses the boundaries of these disciplines.