Role of d-wave pairing in A15A15 superconductors

We argue that the recent Raman spectroscopy observation of a sharp mode in s-wave superconducting V$_3$Si is due to a competing d-wave pairing state. We present microscopic arguments for the origin of this d-wave order. We further argue that the d-wave order explains the observed shrinking of the vortex core structure at anomalously low magnetic fields and the large anisotropy observed in the upper critical field

Test Data Sets for Evaluating Data Visualization Techniques

In this paper we take a step toward addressing a pressing general problem in the development of data visualization systems — how to measure their effectiveness. The step we take is to define a model for specifying the generation of test data that can be em-ployed for standardized and quantitative testing of a system’s per-formance. These test data sets, in conjunction with appropriate testing procedures, can provide a basis for certifying the effective-ness of a visualization system and for conducting comparative studies to steer system development

Low temperature resistivity of Ce‐La‐Th under pressure

The low temperature resistivity of Ce0.9-xLaxTh 0.1 alloys is known to vary as ρ0+αT 2. We have investigated the variation of ρ0 and α with pressure for several concentrations x. An unusually strong nonlinear decrease of the residual resistivity with pressure occurs; the magnitude of the decrease is an order-of-magnitude larger than in the isostructural nonmagnetic alloy La0.8Th0.2. The temperature coefficient α(P) also decreases strongly. These results are in qualitative accord with recent theories of the resistivity of disordered valence fluctuation compounds

Comparing the effects of oxygen content on the superconducting properties of YBa2Cu3Ox and RBa2Cu3Ox ith R = Nd, Eu and Gd

Previous studies have shown that a Josephson weak link transition occurs in some YBa2Cu3Ox samples at very low fields, H < HC1. This transition is distinct from the vortex glass-fluid transition which of course occurs for H > HC1. The Josephson weak link transition for YBa2Cu3Ox was observed only in samples annealed in oxygen. Moreover, the transition temperature Tc of YBa2Cu3Ox is also sensitive to oxygen content. Tc is 93 K for air-sintered and vacuum-annealed samples but only 90 K for oxygen-annealed samples. We have extended these studies to RBa2Cu3Ox samples with R = Nd, Eu and Gd. Like the Y-based systems, all three show the Josephson weak link transition but only for oxygen-annealed samples. Unlike the Y-based system, the values of Tc for RBa2Cu3Ox are not sensitive to oxygen content with Tc being 95 K for all samples. Moreover, the Y- and R-based systems show different specific heat behavior. C/T vs. T for both oxygen and vacuum-annealed RBa2Cu3Ox samples show a single peak at 95 K. Vacuum-annealed YBa2Cu3Ox samples also show a single C/T peak at 93 K, but oxygen-annealed YBa2Cu3Ox samples show two peaks in C/T at 90 and 93 K. © 1999 Elsevier Science B.V. All rights reserved