{mu}SR studies of the vortex state in type-II superconductors

• Published in: Reviews of modern physics Vol. 72; no. 3
• Main Authors: Sonier, Jeff E., Brewer, Jess H., Canadian Institute for Advanced Research, Toronto, Ontario, Canada M5G 1Z8, Kiefl, Robert F.
• Format: Journal Article
• Language: English
• Published: United States 01-07-2000
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; EXPERIMENTAL DATA; GINZBURG-LANDAU THEORY; HIGH-TC SUPERCONDUCTORS; MAGNETIC FIELDS; MUON PROBES; PENETRATION DEPTH; THEORETICAL DATA; TYPE-II SUPERCONDUCTORS; VORTICES
• ISSN: 0034-6861; 1539-0756
• DOI: 10.1103/RevModPhys.72.769

The authors present a review of recent muon spin rotation ({mu}SR) studies of the vortex state in type-II superconductors. There are significant gaps in our understanding of this unusual phase of matter, especially in unconventional superconductors, for which the description of the vortex structure is a subject of great controversy. The {mu}SR technique provides a sensitive local probe of the spatially inhomogeneous magnetic field associated with the vortex state. For the case of a regular vortex lattice, the magnetic penetration depth {lambda} and the coherence length {xi} can be simultaneously extracted from the measured internal field distribution. The penetration depth is directly related to the density of superconducting carriers in the material, and measurements of its variation with temperature, magnetic field, and impurities can provide essential information on the symmetry of the order parameter. The coherence length measured with {mu}SR is the length scale for spatial variations of the order parameter within a vortex core. A primary goal of this review article is to show that measurements of these fundamental length scales are fairly robust with respect to the details of how the field distribution is modeled. The reliability of the results is demonstrated by a comparison of the {mu}SR experiments with relevant theories and with other experimental techniques. The authors also review {mu}SR measurements that have focused on the study of pinning-induced spatial disorder and vortex fluctuation phenomena. The {mu}SR technique has proven to be a powerful tool for investigating exotic vortex phases, where vortex transitions are directly observable from changes in the {mu}SR line shape. Particular emphasis is given to {mu}SR experiments performed on high-temperature superconductors since high-quality single crystals have become available. (c) 2000 The American Physical Society.