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。它们的电子态的独特特征--“壳结构”有序--使得这种团簇在这项研究中尤其有希望成为纳米级的系统。特定大小的颗粒预计会表现出与大块样品相比大大增强的配对，并伴随着临界温度的升高。这意味着一条在史无前例的200K或更高温度下实现超导的途径，可能是在室温下。在该项目的第一阶段，将通过测量作为温度和尺寸的函数的光致电离阈值来精确地确定自由团簇中配对对电子光谱的影响。在第二阶段，将通过将尺寸选定的纳米团簇软着陆在悬浮纳米管上来产生原型电路。沉积的团簇将沿着纳米管形成一个离散的链，纳米管的导电性将受到邻近效应的影响。这种方法将对单个纳米粒子的高度敏感性与调整其参数的能力结合在一起。最终目标是将超导电流容量的数量级增加与工作温度的数量级增加合并，从而促进纳米超导传输的进步和应用。该项目为学生和博士后提供了在一个固有的跨学科领域的广泛实验和理论方面的出色培训。*非技术摘要*100年前发现的超导现象是物理学中最迷人、最复杂、最有用和最重要的效应之一。有些材料在冷却到“临界温度”以下时会完全失去电阻。几十年来，临界温度似乎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，医用核磁共振、粒子加速器)，但昂贵且有限。在过去的二十年里，随着科学家们意识到超导“潜伏”在更多的材料和更高的温度下，这个领域已经蓬勃发展。一个愿望是发现具有更高临界温度的系统，最好是在室温下也是如此。该项目将通过探测纳米团簇中的超导转变，将对高温超导电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，从几十个到数百个，并且可以精确地选择大小。预计一定尺寸的纳米团簇在200开尔文甚至更高的温度下将表现出超导电性，可能达到室温水平。此外，由这种纳米团簇组成的电路可以在没有电阻的情况下传输高电流。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。这一主题对于本科生、小学生和高中生的外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.