The Emergence of Metallic Properties in Free Metal Clusters in a Molecular Beam

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

****NON-TECHNICAL ABSTRACT**** There is an increasing interest in the properties of nanoscopic objects. Yet little is known about the properties of the very smallest metal particles, or clusters, which consist of only a few atoms. It is possible to produce these extremely small particles and to study their properties in a vacuum chamber. This individual investigator award supports a project that will produce a beam of small metallic clusters, which are subsequently cooled to extremely low temperatures. Beams of these particles are then deflected in electric and magnetic fields. The magnetic deflections provide critical information about the magnetic properties of the clusters, which can be compared with magnetic properties of bulk materials. Deflections in electric fields show whether these small metal particles conduct electricity or not. There is some evidence that certain metal clusters have properties akin to superconductivity even at room temperature. These fundamental studies will provide important information about what makes a metal a metal. They will also indicate whether specific metal clusters may be useful for nanotechnology applications such as magnetic recording. Graduate and undergraduate students will learn a variety of experimental techniques that will prepare them for future positions in academia or industry. The training they receive will provide them with the skills needed to become forefront researchers in the properties of nanoscopic electronic objects. This award receives funding from the Division of Materials Research and the Division of Physics. **** TECHNICAL ABSTRACT**** This individual investigator award supports a project that addresses the fundamental question of how metallic properties develop in metallic clusters as a function of size. Beams of small metal clusters with from one to several hundred atoms are produced in a cryogenic cluster source using the pulsed laser vaporization method and their properties are studied in high vacuum as they fly from the source to a position sensitive mass analyzer that can simultaneously measure both the mass and the positions of the clusters. Clusters with temperatures of about 20 K are essentially in their electronic and vibrational ground states and therefore are ideally suited for studying the ground state properties of the material. In the bulk, metals do not tolerate a voltage difference and therefore bulk metal objects cannot have electric dipole moments. Hence electric dipole measurements of small clusters will provide information on the emergence of this important metallic property. Molecular beam electron spin resonance measurements of the magnetic moments of paramagnetic clusters will trace the size evolution of the g-values in small alkali clusters and in niobium clusters. In the latter case these measurements may provide insight into a possible connection between a ferroelectric state and superconductivity. Graduate and undergraduate students will learn a variety of experimental techniques that will prepare them for future positions in academia or industry. The training the receive will provide them with the skills needed to become forefront researchers in the properties of nanoscopic electronic objects. This award receives funding from the Division of Materials Research and the Division of Physics.