Paired Radical States in Molecular Wires: 1D Topological Insulators and Beyond

非技术描述：由于其在电子应用、光伏和人工光合作用中的重要作用，人们已经投入了大量的精力来开发能够在纳米尺度上有效传输电荷的分子。然而，大多数充当导线的分子随着其长度的增加，电导率呈指数下降，从而限制了它们的潜在应用。该研究项目的目标是开发基于分子的电子电路，该电路可以使用带有未配对电子（自由基）的分子导线远距离传导电荷。因此，这项研究将解决开发长而高导电性的全有机分子线的挑战。此外，该项目将提供新的设计策略来稳定分子内的自由基；这些策略可能会对分子量子比特和量子计算等新兴领域产生影响。除了推进纳米级电子学的应用之外，该项目旨在激发K-12儿童和本科生的兴趣，并吸引他们进入STEM领域，特别是那些代表性不足的少数民族学生和女性，这将通过指导来实现，在多学科环境中提供本科生研究经验，并通过服务项目影响研究生招生。技术描述：分子导线的传导遵循相干和非谐振机制，随着长度的增加，电导率呈指数下降，这使得它们不适合需要高导电性长的导线的应用。克服这一限制的一种方法是设计和构建具有一对基态的一维拓扑绝缘子线。这些导线通过其基于激进的独特边界（或边缘）状态传导，而其内部保持绝缘。这样的导线会导致电导随着导线长度的增加而增加。本项目旨在通过理论与实验相结合的方法来设计、创造、测量和理解这些分子导线中的电子输运。该项目的三个具体目标是：(1)探测具有单个自由基对的导线中的输运，并了解这些状态与源极和漏极之间的电子耦合如何控制输运；(2)制作具有多个自由基对的导线，并研究电导随长度的变化；(3)设计具有多个自由基对的循环导线，探索量子干涉和自旋对输运的影响。该项目的教育和推广工作也有三个主要目标：(1)在多学科环境中提供本科生研究机会；(2)将研究融入应用物理本科教育；(3)让K-12学生参与实验室活动，向他们介绍纳米科学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description:Significant efforts have been invested to develop molecules that can transport charge efficiently at nanometer scale, driven by their important for electronic application, photovoltaics and artificial photosynthesis. However, most molecules that act as conducting wires show an exponential decrease in conductance as their lengths increase, thus limiting their potential applications. The objective of this research project is to develop molecule-based electronic circuits that can conduct charge over long distances using molecular wires with un-paired electrons (radicals). This research will therefore address the challenge of developing long and highly conductive all-organic molecular wires. Further, this project will provide new design strategies to stabilize radicals within molecules; these strategies are likely to have impact in the emerging area of molecular qubits and quantum computing. Beyond advancing applications in nanoscale electronics, this project seeks to excite K-12 children and undergraduate students and attract them in STEM fields, particularly those who are underrepresented minority students and women, which will be pursued through mentoring, providing undergraduate research experiences in a multidisciplinary environment, and influencing the graduate admissions through service programs.Technical description:Molecular wires that conduct following a coherent and off-resonant mechanism exhibit an exponential decrease in conductance with increasing length, making them impractical for applications where highly conductive long wires are required. One way to overcome this limitation is to design and construct one-dimensional topological insulator wires with a pair of radical states. These wires conduct through their radical-based unique boundary (or edge) states, while their interior remains insulating. Such wires could result in a conductance that increases with wire length. This project aims to design, create, measure, and understand electronic transport in these molecular wires by combining theory and experiment. The three specific objectives of the project are: (1) To probe transport in wires with a single radical pair and understand how the electronic coupling between these states and the source and drain electrodes control transport; (2) To create wires with multiple radical pairs and investigate how conductance changes with length; and (3) To design cyclic wires with multiple radical pairs to explore the effects of quantum interference and spin on transport. The educational and outreach efforts of this project also have three broad objectives: (1) To provide undergraduate research opportunities in a multidisciplinary environment; (2) To integrate research into the Applied Physics undergraduate education and (3) To engage K-12 students in laboratory activities and introduce them to nanoscience.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.