Harlingen This experimental research project focuses on the role of long- range phase coherence in superconductor materials and devices. The work is based on the SQUID interferometry techniques the PI has developed to detect the phase of the order parameter in single crystal superconductor samples; and on the use of a scanning SQUID microscope (SSM). Three areas of proposed research include: (1) Use of the SSM to study vortex configurations and dynamics in superconductor arrays. (2) Application of the SQUID interferometry methods to identify the order parameter symmetry in heavy fermion superconductors and in organic superconductors, both types of material showing indications of unconventional pairing. (3) Magnetic imaging of hybrid systems consisting, e.g.,of alternating arrays of d-wave and s-wave islands. %%% This experimental research project, at the forefront of research in unconventional types of superconductivity, focuses on the "phase coherence" property of superconductors and superfluids in general. The most useful properties of superconductors: the superfluid (lossless) electrical conduction, and the Superconducting Quantum Interference Device (SQUID) magnetic field sensors and fast logic elements, all arise from phase coherence. It has recently been found with high probability that the phase-coherent properties of the high Tc cuprate superconductors are strikingly different from those of conventional superconductors, like lead and NbTi. This research project is devoted in part to the phase properties of additional types of superconductors, organic metals and "heavy fermion" superconductors, which may also exhibit unconventional phase behavior. Portions of this research will utilize a Scanning Squid Microscope, which can measure local m agnetic fields at the level of one billionth of an Oersted (1/2 Oersted is about the level of the earth's magnetic field) with a spatial resolution of about 100 micrometers. Results from this research may include unusual new effects or structures which may find application in technology. This research project is interdisciplinary in nature and involves graduate students who will be excellently trained to enter positions in industry, government or education. ***
