Studies with Liquid Helium Films

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

This low temperature project seeks to understand the unique properties of helium films and to use these films to address problems of interest in Condensed Matter Physics. A primary objective is to study new aspects of the He-3-He-4 mixture film system. This work would include confirmation of two-dimensional Fermi liquid parameters and a search for a new superfluid state in the two dimensional 3He atop a 4He film at very low temperatures. Experiments are also conducted with helium films on patterned substrates in one and two dimensions. Topics of interest include two-dimensional localization and a possible shift of universality class due to an implied film flow. Experimental techniques include quartz crystal microbalance resonance, heat capacity studies of the thermal properties of He-4 and He-3-He-4 mixture films, and third sound studies of helium films on patterned substrates. In addition to contributing to progress in understanding the behavior of helium films themselves, the work has relevance to phenomena such as Fermi systems, localization, and two-dimensional phase transitions. It also provides excellent training for graduate students and undergraduates. The students gain experience in cutting edge technology and fundamental concepts that prepare them for careers in academe, government or industry. This research investigates the remarkable properties of liquid helium. Such study provides unique insights into nature that are not available by the study of any other substance. Study of the wave character of thin helium films on surfaces, that have been deliberately patterned, allows an enhanced understanding of how waves can be trapped in novel environments and of how an imposed flow can modify this behavior. The study of thin film mixtures of the two naturally occurring forms of helium is motivated by theoretical suggestions that a new kind of superfluid film may be found. These studies with mixture films also allow insight into the physics of two-dimensional systems. Students involved in this work gain hands-on research experience with sophisticated instrumentation. This training prepares them for careers in academe, government or industry.