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

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

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).