Ultrasonics Of High Tc And Other Unconventional Superconductors

Physical Acoustics, Volume XX: Ultrasonics of High-Tc and Other Unconventional Superconductors covers the many acoustic studies of the high-Tc superconductors. This book is composed of 10 chapters that include some unconventional superconducting systems, such as superfluid 3He, heavy Fermion superconductors, and magnetic re-entrant superconductors. The introductory chapter summarizes the results that have been observed in Bardeen, Cooper, and Schriefer superconductors as functions both of temperature and magnetic field. The subsequent chapters deal with the theoretical and experimental aspects of ultrasonic study of some unconventional superconductors. Considerable chapters are devoted to the measurements with sound waves on the sintered high-Tc superconducting systems. These chapters examine first the temperature and magnetic field dependence of the velocity and elastic constants in sintered high-Tc superconductors, as well as the sound absorption and dispersion measurements on single crystals of these superconductors. Discussions on the small-sample resonant ultrasound technique that uses thin piezoelectric films and the effect of oxygen on superconducting properties and the response of sound to these additions are also provided in these chapters. The concluding chapter presents a theoretical foundation for sound measurements in the superconducting state, emphasizing the effects of multigap structures and gas anisotropy on sound attenuation in the superconducting state of the cuprate superconductors. This volume will be of great benefit to researchers in the fields of electronics technology and in applied and engineering mechanics.

Author index.

Ultrasonic techniques have been used to characterize the properties of high Tc superconductors. A model is being developed to explain the radiation losses from a resonating fused silica sample. A new very sensitive resonant technique was developed for studying vortex motion in the superconducting state of an untwinned single crystal of YBCO. Evidence is obtained for a transition from a soft vortex system to a rigid strongly interacting vortex system in the vicinity of the superconducting transition temperature. A percolation model developed in our group to describe surface acoustic wave attenuation in a granular superconducting film was modified to include the resistivity of the individual grains in a matrix of Josephson junctions. SAW measurements using a pontoon technique on both a single crystal and a thin film of YBCO demonstrate the importance of pinning sites in determining the nature of a vortex transition; the vortex system will undergo a depinning transition if the pinning density is large and a melting transition if it is small. Resonant ultrasonic spectroscopy data obtained as a function of gas pressure has been analyzed.

Physical Phenomena at High Magnetic Fields IV (PPHMF-IV) was the fourth in the series of conferences sponsored by the National High Magnetic Field Laboratory (NHMFL). The success of PPHMF-I, II and III, held in 1991, 1995 and 1998 respectively, encouraged the organizers to once again bring together experts in scientific research areas where high magnetic fields play an important role, to critically assess the current status of research in these areas, and to discuss promising new directions in science, as well as applications which are in the forefront of these fields.

Ultrasonic techniques have been used to characterize properties of high T sub c and other unconventional superconductors. Attenuation and velocity measurements with shear waves have been performed on a sintered sample of HgBa2CuO4 and single crystal and melt textured samples of YBCO as a function of magnetic field. Anomalous behavior is observed which may be due to the fact that sound waves are sensitive to the total number of flux lines sampled, regardless of their orientation. A pontoon technique was used to launch surface acoustic waves SAW through a single crystal platelet of YBCO. A relative maximum in attenuation is observed at around 90K which may be associated with a relaxation process. Measurements on a SAW reflective array compressor made of superconducting YBCO appear to indicate that the YBCO reflecting chevrons are more effective in reflecting the SAW in the normal state than in the superconducting state. The insertion loss of a SAW delay line made with YBCO interdigital electrodes decreased when the electrodes became superconducting. A theoretical model has been developed to quantitatively explain these results.

“The Frontiers of Knowhledge (to coin a phrase) are always on the move. - day’s discovery will tomorrow be part of the mental furniture of every research worker. By the end of next week it will be in every course of graduate lectures. Within the month there will be a clamour to have it in the undergraduate c- riculum. Next year, I do believe, it will seem so commonplace that it may be assumed to be known by every schoolboy. “The process of advancing the line of settlements, and cultivating and c- ilizing the new territory, takes place in stages. The original papers are p- lished, to the delight of their authors, and to the critical eyes of their readers. Review articles then provide crude sketch plans, elementary guides through the forests of the literature. Then come the monographs, exact surveys, mapping out the ground that has been won, adjusting claims for priority, putting each fact or theory into its place” (J. M. Ziman, Principles of the Theory of Solids (Cambridge University Press, 1972) p.v). The main purpose of the book is to present the mechanism of - perconductivity discovered in 1986 by J. G. Bednorz and K. A. Müller, and to discuss the physics of superconductors. The last chapter of the book presents analysis of tunneling measurements in cuprates. The book is - dressed to researchers and graduate students in all branches of exact sciences.

This is the first monograph that strives to give a complete and detailed description of the collective modes (CMs) in unconventional superfluids and superconductors (UCSF&SC). Using the most powerful method of modern theoretical physics OCo the path (functional) integral technique OCo authors build the three- and two-dimensional models for s -, p - and d -wave pairing in neutral as well as in charged FermiOCosystems, models of superfluid BoseOCosystems and FermiOCoBoseOComixtures. Within these models they study the collective properties of such systems as superfluid 3 He, superfluid 4 He, superfluid 3 He- 4 He mixtures, superfluid 3 He-films, superfluid 3 He and superfluid 3 He- 4 He mixtures in aerogel, high temperature superconductors, heavy-fermion superconductors, superconducting films etc. Authors compare their results with experimental data and predict a lot of new experiments on CMs study. This opens for experimentalists new possibilities for search of new intriguing features of collective behavior of UCSF&SC. The monograph creates the new scientific direction OCo the spectroscopy of collective modes in unconventional superfluids and superconductors. It will be useful for both theorists and experimentalists, studying superfluids and superconductors, low temperature physics, condensed matter physics, solid state physics. It could be used by graduate students specializing in the same areas. Sample Chapter(s). Introduction (162 KB). Chapter 1: Functional Integration Method (369 KB). Contents: Functional Integration Method; Collective Excitations in Superfluid Fermi-Systems with s OCoPairing; Superfluid Phases in 3 He; The Model of 3 He; Collective Excitations in the B OCoPhase of 3 He; Collective Excitations in the A OCoPhase of 3 He; Stability of Goldstone Modes; Influence of Dipole Interaction and Magnetic Field on Collective Excitations; The Influence of the Electric Field on the Collective Excitations in 3 He and 4 He; The Order Parameter Distortion and Collective Modes in 3 HeOCo B; Collective Excitations in the Planar 2 D OCoPhase of Superfluid 3 He; Collective Excitations in the PolarOCoPhase; Superfluidity of TwoOCoDimensional and One-Dimensional Systems; BoseOCoSpectrum of Superfluid Solutions 3 He- 4 He; Novel Sound Phenomena in Impure Superfluids; Collective Modes in the HeavyOCoFermion Superconductors; Other Application of the Theory of Collective Excitations. Readership: Graduate and postgraduate students, researchers (theorists and experimentalists), in low temperature physics, superconductivity and condensed matter physics."