147 research outputs found
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 .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
Free jejunal flap reconstruction of the cervical oesophagus in a patient with laryngeal cancer recurrence after laryngectomy and radiotherapy - a case report
Time-Distance Helioseismology of Deep Meridional Circulation
A key component of solar interior dynamics is the meridional circulation
(MC), whose poleward component in the surface layers has been well observed.
Time-distance helioseismic studies of the deep structure of MC, however, have
yielded conflicting inferences. Here, following a summary of existing results
we show how a large center-to-limb systematics (CLS) in the measured travel
times of acoustic waves affect the inferences through an analysis of frequency
dependence of CLS, using data from the Helioseismic and Doppler Imager (HMI)
onboard Solar Dynamics Observatory (SDO). Our results point to the residual
systematics in travel times as a major cause of differing inferences on the
deep structure of MC.Comment: 6 pages, 3 figures, to appear in the Springer series Astrophysics and
Space Science Proceedings of "Dynamics of the Sun & Stars: Honoring the Life
& Work of Michael Thompson" (2020
Electrical anisotropy in high-Tc granular superconductors in a magnetic field
We propose an analytical model devoted to explain the anisotropy of the electrical resistance observed below the critical temperature in granular high-Tc superconductors submitted to a magnetic field H. Reported experimental results obtained on a YBCO sample show that the superconducting transition occurs in two stages, with a steep drop of the resistance at Tc and a subsequent, smoother decrease. In this second stage, the resistance versus temperature curve is strongly dependent not only on the field intensity, but also on the angle between H and the macroscopic current density j. We start from the assumption that the resistance below Tc is mainly due to the weak links between grains. In the model, weak links are thought of as flat surface elements separating adjacent grains. We calculate the probability for a weak link to undergo the transition to the resistive state as a function of the angle it makes with the external magnetic field H and the macroscopic current density j. In doing this, an important role is given to the strong nonuniformity of the local magnetic field within the specimen, due to the effect of the screening supercurrents flowing on the surface of the grains. Finally, we calculate the electrical resistance of the sample in the two cases H⊥j and H∥j. The predictions of this simple model turn out to be in reasonable agreement with reported experimental results obtained on a YBCO granular specimen
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