Direct observation of vortices in the organic superconductorκ−(BEDT−TTF)2Cu(NCS

Abstract

Results of direct imaging of Abrikosov vortices in an organic superconductor by means of the decoration technique are presented. The vortices have been observed in the title compound at temperature of Ӎ0.5T c at the magnetic fields 3.3-9.4 Oe directed perpendicular to the two-dimensional plane of the crystal. The decoration patterns reveal the sixfold coordination short-range order or slightly distorted triangular lattice of the vortices with the magnetic flux per vortex equal to the flux quantum, hc/2e. The slight deviation of the vortex lattice from the hexagonal symmetry is attributed to the in-plane anisotropy of the penetration depth. The average size of the individual vortex images on the sample surface yields the upper limit estimation of the London penetration depth as 0.4 m at the given temperature. Pronounced effects of pinning on the crystal defects and thermally activated mobility of the vortices have been observed.

Muon-Spin Rotation Studies of Electronic Properties of Molecular Conductors and Superconductors

“…The field dependence of β at 2 K is shown in Figure a and shows a crossover from a value consistent with a trangular Abrikosov vortex structure (β = 0.60) to a symmetric line shape. Flux decoration experiments have confirmed the presence of a triangular vortex lattice at fields below 1 mT . The breakup of the interlayer order above 5 K is shown in the temperature dependence of β in Figure b.…”