Research Highlight: Pinning in High-Temperature Superconductors (HTSC).

1. Theory of Superconducting and Electromagnetic Properties of Some Nanostructured MaterialsDavid Stroud, Ohio State University, DMR 0413395 • Research Highlight: Pinning in High-Temperature Superconductors (HTSC). • A HTSC can carry current with NO resistance up to about one-half of room temperature, but only if current swirls, called vortices, can be pinned. • In HTSC, we showed that this pinning occurs in regions of locally ``good’’ superconductor. This is opposite from low-temperature superconductors. • May be very important for applications (eg HTSC wires). Left: sketch of a HTSC layer. Good (beta) regions (white) are scattered among less good (alpha) regions (gray). Vortex (red) pinned near beta regions. Above: calculated density of states in the vortex (beta region) and away from the vortex (alpha). Agrees with experiment. (Valdez-Balderas and Stroud, submitted for publication).

2. Possible applications: novel ways of pinning vortices in HTSC – hence, of generating large currents without resistance. Could be used to make superconductors work in higher magnetic fields – better MRI devices? References: D. Valdez-Balderas and D. Stroud, Phys. Rev. B74, 174506 (2006) and submitted to Phys. Rev. B. Contributions to education: seven grad students (D. Valdez-Balderas, I. Tornes, K. Kim, V. Guttal, R. Tiwari, C. Porter, K. Kobayashi), two undergrads (B. Chen from Harvard, S. Natu from Ohio Wesleyan) contributed to this work. Ivan Tornes is now a researcher at Battelle, D. Valdez-Balderas and K. Kim have postdocs at Rochester and Maryland. Work done under this grant was included in courses on Quantum Computing and Condensed Matter Physics Theory of Superconducting and Electromagnetic Properties of Some Nanostructured Materials David Stroud, Ohio State University, DMR 0413395