Electron Pairing and Spin Dynamics in Metal Clusters at Low Temperatures in a Molecular Beam

团簇物理学从物质的角度来看，当团簇的大小一次增加一个原子，直到达到体积极限时，材料的性质就会系统地发展。这种方法对简单金属团簇系统的物理性质产生了重要的新见解。该个人研究者奖支持一个项目，解决两个基本问题：铁磁团簇系统中绝热自旋弛豫过程的物理学和顺磁团簇系统中的配对相关性。(1)使用分子束偏转方法探测的绝热自旋弛豫过程在所有研究的铁磁团簇系统中都观察到，但介导这一过程的机制尚不清楚。(2)低温下簇束偏转显示铌簇的电偶极极化率存在较大的奇偶振荡，并伴有异常大的永久电偶极矩。这表明了一个具有强电子配对相关性的对称破碎的低温接地相，表明了新生的超导性。对这些效应的束束研究将对理解小系统中的电子相关性和自旋动力学产生深远的影响。参与该项目的研究生接受尖端技术的基础实验技术培训。这种培训将为他们在学术界、工业界或政府的一系列职业生涯做好准备。该项目由材料研究部（凝聚态物理）和物理部（原子、分子和光学物理）联合支持。团簇物理学的观点是，当原子团簇的大小一次增加一个原子，直到达到体积极限时，材料的性质就会系统地发展。重要的是要探索一块材料在多大的尺寸变得足够小，以至于它失去了“正常”的体积行为。此外，通过研究那些足够小而不像大块物质那样表现的星团，人们可能会发现一些新奇有趣的现象。为这个项目开发的最先进的分子束方法非常适合探测这些极小的簇：在一个新的超低温脉冲激光簇源中，几乎任何金属的簇都可以在10 K到300 K的温度下产生。这个项目将研究非常小的金属原子簇的磁性和电学性质。在低温下，电荷自发地在铌、钒和钽簇中分离。这可能表明超导现象正在形成。这些效应的研究将对理解这些重要材料的超导性和相关的电子效应具有深远的意义。参与该项目的研究生接受尖端技术的基础实验技术培训。这种培训将为他们在学术界、工业界或政府的一系列职业生涯做好准备。该项目由材料研究部（凝聚态物理）和物理部（原子、分子和光学物理）联合支持。

Cluster physics approaches matter from the standpoint that material properties evolve systematically when clusters are increased in size one atom at a time until the bulk limit is reached. This approach has yielded important new insights into the physical properties of simple metal cluster systems. This individual investigator award supports a project addressing two fundamental problems: the physics of adiabatic spin-relaxation processes in ferromagnetic cluster systems and pairing correlations in paramagnetic cluster systems. (1) Adiabatic spin-relaxation processes, probed using molecular beam deflection methods, have been observed in all ferromagnetic cluster systems studied yet there the mechanism that mediates this process is unknown. (2) Cluster beam deflections at low temperatures reveal large even-odd oscillations in the electric dipole polarizabilities of niobium clusters, which are accompanied by exceptionally large permanent electric dipole moments. This indicates a symmetry-broken ground low temperature phase with strong electron-paring correlations, suggesting nascent superconductivity. Cluster beam investigations of these effects will have far-reaching consequences in the understanding of electronic correlations and spin dynamics in small systems. Graduate students involved in the project receive training in fundamental experimental techniques with cutting edge technology. This training will prepare them for a range of careers in academe, industry or government. The project is jointly supported by the Divisions of Materials Research (Condensed Matter Physics) and Physics (Atomic, Molecular, and Optical Physics).Cluster physics approaches matter from the standpoint that material properties evolve systematically when clusters of atoms are increased in size one atom at a time until the bulk limit is reached. It is important to explore at what size a piece of material becomes small enough that it looses its "normal," bulk behavior. In addition by studying clusters which are small enough not have behave like the bulk material, one may discover novel interesting phenomena. The state of the art molecular beam methods developed for this project are ideally suited to probe these extremely small clusters: clusters of virtually any metal can be produced at temperatures from 10 K to 300 K in a new ultra-low temperature pulsed-laser cluster-source. This project will investigate the magnetic and electric properties of very small clusters of metal atoms. At low temperatures, the electric charge spontaneously separates in niobium, vanadium and tantalum clusters. This may suggest nascent superconductivity. Investigations of these effects are proposed and they will have far-reaching implications in the understanding superconductivity and related electronic effects in these important materials. Graduate students involved in the project receive training in fundamental experimental techniques with cutting edge technology. This training will prepare them for a range of careers in academe, industry or government. The project is jointly supported by the Divisions of Materials Research (Condensed Matter Physics) and Physics (Atomic, Molecular, and Optical Physics).