Ginzburg-Landau parameter inYBa2Cu3

T. M. Riseman

¹

,

J. H. Brewer

²

,

K. H. Chow

³

et al.

Abstract

The vortex state of a type-II superconductor produces a distinctive @+SRline shape with features determined by the average internal Beld Ho, the magnetic penetration depth A, the superconducting coherence length (, and the degree of disorder in the vortex lattice. Only in the high field regime (A )) L ) (, where L is the intervortex spacing) do the vortex cores (of radius () occupy a large enough area that they are observable in the line shape as a high field cutoff. Our @+SR measurements of the field distributions in a mosaic of single crystals of YBa2Cu306. g5 in fields of 1.9, 4.1, 4.7, and 6.5 T (Bo~~c) show all the features of the line shape. We find A = 0.15+0.01 pm at 10 K and the Ginzburg-Landau parameter r-: A/( = 69.6 + 1.4 constant between 30 and 75 K; this is the only measurement to date of K in YBa2Cu306. g5 below the irreversibility temperature. Due to disorder in the vortex lattice, either from pinning or from vortex Quctuations that are quasistatic on the time scale of @+SR, the observed line shape is "smeared" relative to that predicted for a perfect lattice. From the degree of smearing, we estimate an upper limit of 5.5% for the rms deviation of individual vortices from their ideal positions. requires no such assumptions in calculating n(B). The effects of the Fermi surface, strong coupling, 8or d-wave pairing, and so on may be inferred &om the temperature dependence found for A and (. Moreover, the modified London model is much faster to calculate.The distribution n(B) is very asymmetric (see Fig.

Vortex States of Tl2Ba2CuO6+δStudied via205Tl NMR at 2 Tesla

“…However, the observed negative shift indicates that a Redfield pattern of a superconducting diamagnetic shift sc K c,dia (ν) is predominant. The T =5 K NMR spectrum resembles the field distribution due to a slightly distorted vortex lattice [14,15] but not a Gaussian due to amorphous vortex or vortex glass. We could not deduce from the NMR spectrum which the vortex lattice is, triangular or square.…”

Anisotropic superconducting properties of single-crystallineFeSe0.5Te0.5

“…(5) Here A 0 and φ are the initial asymmetry and the phase of the muon spin ensemble, respectively, σ g is a parameter related to the FLL disorder, 42,43 σ nm is the nuclear moment contribution measured at T > T c , which is generally temperature independent, 44 and Λ e is the relaxation rate of the electronic moment contribution, which was obtained from the measurements taken above T c .…”

Supercooled vortex liquid and quantitative theory of melting of the flux-line lattice in type-II superconductors

“…There is no consensus on values of κ measured using the microwave technique at very low temperatures, however they are also generally smaller than 100 (smaller than 70 at T = 0 and decreasing with temperature according to ref. [63] and from 50 to 60 in ref. [64]).…”