Nanoclusters with High-Temperature Superconducting Pairing: Detection and Deposition

****技术摘要****该项目涉及由数十到数百个原子组成的纳米团簇中的高温超导配对。它们的电子状态的独特特征——“壳结构”有序——使这种团簇成为这项研究中特别有前途的纳米级系统。特定尺寸的颗粒预计会显示出相对于散装样品大大增强的配对，并伴随临界温度的增加。这意味着在前所未有的200k或更高的温度下，可能在室温下，有一条通往超导的道路。在项目的第一阶段，配对对电子光谱的影响将通过测量光电离阈值作为温度和尺寸的函数来确定。在第二阶段，原型电路将通过在悬浮纳米管上软着陆选定尺寸的纳米团簇来生产。沉积的团簇将沿纳米管形成离散链，并且纳米管的电导率将因邻近效应而改变。这种方法结合了对单个纳米粒子的高灵敏度和调整其参数的能力。最终目标是将超导电流容量的数量级增长与工作温度的数量级增长结合起来，从而导致纳米级超导传输的进步和应用。该项目为学生和博士后提供了广泛的跨学科领域的实验和理论方面的优秀培训。****非技术摘要**** 100年前发现的超导现象是物理学中最引人入胜、最复杂、最有用和最重要的现象之一。一些材料在冷却到“临界温度”以下时完全失去电阻。几十年来，似乎临界温度可能被限制在非常低的值，接近绝对零度。因此，应用是有价值的（例如，医学磁共振成像，粒子加速器），但昂贵和有限。在过去的二十年里，随着科学家们意识到超导性“潜伏”在更多的材料和更高的温度中，这个领域得到了蓬勃发展。一个愿望是发现具有更高临界温度的系统，甚至在室温下也是理想的。该项目将通过探测纳米团簇中的超导转变，将高温超导性的追求与纳米科学领域相结合，从而推进这一目标。纳米团簇是有限数量的金属原子的聚集体，从几十个到几百个，可以精确地选择大小。预计一定尺寸的纳米团簇将在200开尔文甚至更高的温度下显示超导性，可能达到室温水平。此外，由这种纳米团簇构成的电路可以无电阻地传输大电流。参与该项目的研究生、本科生和博士后将接受与这一跨学科科学领域相关的广泛技能培训。这个主题对于本科生、小学和高中学生的拓展项目也是富有成效的。

****Technical Abstract****The project is concerned with high-temperature superconducting pairing in nanoclusters composed of tens to hundreds of atoms in size. The distinct character of their electronic states - "shell structure" ordering - makes such clusters especially promising nanoscale systems for this research. Particles of specific sizes are anticipated to display pairing that is greatly enhanced relative to bulk samples, with a concomitant increase in the critical temperature. The implication is a path towards superconductivity at unprecedented temperatures of 200 K or higher, possibly at room temperature. In the first stage of the project, the influence of pairing on the electronic spectrum will be pinpointed in free clusters by a measurement of photoionization thresholds as a function of temperature and size. In the second stage, prototype circuits will be produced by soft-landing size-selected nanoclusters on suspended nanotubes. The deposited clusters will form a discrete chain along the nanotube, and the nanotube's conductivity will be modified by the proximity effect. This approach combines high sensitivity to individual nanoparticles with the ability to tune their parameters. The ultimate goal is to merge an orders-of-magnitude increase in superconducting current capacity with an orders-of-magnitude increase in the operating temperature, leading to advances in, and applications of, nanoscale superconducting transport. The project offers students and postdocs excellent training in a wide range of experimental and theoretical aspects of an inherently interdisciplinary field.****Non-Technical Abstract****The phenomenon of superconductivity, discovered 100 years ago, is one of the most fascinating, complex, useful and important effects in physics. Some materials completely lose their electrical resistance when cooled below their "critical temperature." For many decades it appeared that critical temperatures may be limited to very low values, close to the absolute zero. Thus applications were valuable (e.g., medical MRI, particle accelerators) but expensive and limited. In the last twenty years the field has blossomed, as scientists realized that superconductivity "lurks" in many more materials and at higher temperatures. An aspiration is to discover systems with still higher critical temperatures, desirably even at room temperature. This project will advance this goal by combining the pursuit of high-temperature superconductivity with the realm of nanoscience, by detecting the superconducting transition in nanoclusters. Nanoclusters are aggregates of a finite number of metal atoms, from tens to hundreds, and can be precisely size-selected. It is anticipated that nanoclusters of certain sizes will display superconductivity at temperatures of 200 Kelvin or even higher, possibly reaching room temperature levels. Furthermore, circuits built out of such nanoclusters can transmit high currents without resistance. The graduate and undergraduate students and postdocs participating in the project will receive training in a wide range of skills associated with this interdisciplinary field of science. The subject matter is also fruitful for outreach programs for undergraduate, elementary-school, and high-school students.