Pairing symmetry signatures of T1 in superconducting ferromagnets

We study the nuclear relaxation rate 1/T1 as a function of temperature for a superconducting-ferromagnetic coexistent system using a p-wave triplet model for the superconducting pairing symmetry. This calculation is contrasted with a singlet s-wave one done previously, and we see for the s-wave case that there is a Hebel-Slichter peak, albeit reduced due to the magnetization, and no peak for the p-wave case. We then compare these results to a nuclear relaxation rate experiment on UGe2 to determine the possible pairing symmetry signatures in that material. It is seen that the experimental data is inconclusive to rule out the possibility of s-wave pairing in $UGe_{2}$.Comment: 4 pages, 4 figure

Physical properties of ferromagnetic-superconducting coexistent system

We studied the nuclear relaxation rate 1/T1 of a ferromagnetic-superconducting system from the mean field model proposed in Ref.14. This model predicts the existence of a set of gapless excitations in the energy spectrum which will affect the properties studied here, such as the density of states and, hence, 1/T1. The study of the temperature variation of 1/T1(for T<Tc) shows that the usual Hebel-Slichter peak exists, but will be reduced because of the dominant role of the gapless fermions and the background magnetic behavior. We have also presented the temperature dependence of ultrasonic attenuation and the frequency dependence of electromagnetic absorption within this model. We are successful in explaining certain experimental results.Comment: 10 Pages, 9 figute

Weakly correlated electrons on a square lattice: a renormalization group theory

We study the weakly interacting Hubbard model on the square lattice using a one-loop renormalization group approach. The transition temperature T_c between the metallic and (nearly) ordered states is found. In the parquet regime, (T_c >> |mu|), the dominant correlations at temperatures below T_c are antiferromagnetic while in the BCS regime (T_c << |mu|) at T_c the d-wave singlet pairing susceptibility is most divergent.Comment: 12 pages, REVTEX, 3 figures included, submitted to Phys. Rev. Let

Relationship between threshold and suprathreshold perception of position and stereoscopic depth.

We seek to determine the relationship between threshold and suprathreshold perception for position offset and stereoscopic depth perception under conditions that elevate their respective thresholds. Two threshold-elevating conditions were used: (1) increasing the interline gap and (2) dioptric blur. Although increasing the interline gap increases position (Vernier) offset and stereoscopic disparity thresholds substantially, the perception of suprathreshold position offset and stereoscopic depth remains unchanged. Perception of suprathreshold position offset also remains unchanged when the Vernier threshold is elevated by dioptric blur. We show that such normalization of suprathreshold position offset can be attributed to the topographical-map-based encoding of position. On the other hand, dioptric blur increases the stereoscopic disparity thresholds and reduces the perceived suprathreshold stereoscopic depth, which can be accounted for by a disparity-computation model in which the activities of absolute disparity encoders are multiplied by a Gaussian weighting function that is centered on the horopter. Overall, the statement equal suprathreshold perception occurs in threshold-elevated and unelevated conditions when the stimuli are equally above their corresponding thresholds describes the results better than the statement suprathreshold stimuli are perceived as equal when they are equal multiples of their respective threshold values

Quasiparticle dynamics and phonon softening in FeSe superconductors

Quasiparticle dynamics of FeSe single crystals revealed by dual-color transient reflectivity measurements ({\Delta}R/R) provides unprecedented information on Fe-based superconductors. The amplitude of fast component in {\Delta}R/R clearly tells a competing scenario between spin fluctuations and superconductivity. Together with the transport measurements, the relaxation time analysis further exhibits anomalous changes at 90 K and 230 K. The former manifests a structure phase transition as well as the associated phonon softening. The latter suggests a previously overlooked phase transition or crossover in FeSe. The electron-phonon coupling constant {\lambda} is found to be 0.16, identical to the value of theoretical calculations. Such a small {\lambda} demonstrates an unconventional origin of superconductivity in FeSe.Comment: Final published version; 5 pages; 4 figure

Robustness of a local Fermi Liquid against Ferromagnetism and Phase Separation

We study the properties of Fermi Liquids with the microscopic constraint of a local self-energy. In this case the forward scattering sum-rule imposes strong limitations on the Fermi-Liquid parameters, which rule out any Pomeranchek instabilities. For both attractive and repulsive interactions, ferromagnetism and phase separation are suppressed. Superconductivity is possible in an s-wave channel only. We also study the approach to the metal-insulator transition, and find a Wilson ratio approaching 2. This ratio and other properties of Sr_{1-x}La_xTiO_3 are all consistent with the local Fermi Liquid scenario.Comment: 4 pages (twocolumn format), can compile with or without epsf.sty latex style file -- Postscript files: fig1.ps and fig2.p