NMR Studies of Density Wave Phases, Superconductivity, and Polymer Electronic Conduction

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

This individual investigator award is to a senior faculty member for experimental investigations using NMR to measure the microscopic static and dynamic properties of the electrons that govern the key properties of superconductors, density wave materials, and conducting polymers. The project includes electrical transport and ESR measurements, often concurrently with the NMR. The measurements will be performed at extremes of temperature, pressure, and magnetic field. The studies in superconductivity include rf-induced flux lattice annealing using NMR spin echoes and measurements of apparently p-wave superconductivity in the organic conductor (TMTSF)(2)PF(6) under pressure. Experiments on density wave materials will include the study of the magnetic field-induced spin-density wave (SDW) phase of (TMTSF)(2)PF(6) under pressure, investigation of thermal SDW phasons below 4 K in (TMTSF)(2)P(1-x)As(x)F(6) to resolve the conflict in interpreting the SDW, and measurement of repinning dynamics. NMR and ESR will be used to investigate the mechanisms for electron charge propagation and the role of disorder in "metallic" and metal-insulating polypyrrole-PF(6). High frequency NMR instrumentation that benefits this research and the larger user community will be developed. This mix of instrumentation techniques and challenging research problems will provide valuable preparation of the participating students and postdocs for their future academic or industrial careers. %%% This individual investigator award is to a senior faculty member for a project that uses nuclear magnetic resonance, electron spin resonance, and electrical transport to study the properties of electrons in several materials, such as superconductors, density wave systems, and an electrically conducting polymer. Many of the measurements involve extremes of high field, high frequency, high pressure, and low temperatures, along with some development of the instrumentation to carry them out. One of the major goals of this project is to investigate the response of collective electron states, such as vortices in superconductors and pinned density waves in quasi one-dimensional materials, to an external driving force. Other goals are to explore the unusual superconducting state of an organic superconductor under pressure and to determine the microscopic mechanisms of electrical conduction in a conducting polymer. Results gained from this work should contribute to knowledge of the basic physics that forms the underpinning for using superconductivity and conducting polymers in technical applications. The advances of magnetic resonance instrumentation into extremes of parameter space will benefit other groups exploiting these methods. This mix of instrumentation techniques and challenging research problems will provide valuable preparation of the participating students and postdocs for their future academic or industrial careers. ***