Dresden 2006 – scientific programme
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TT: Tiefe Temperaturen
TT 33: Superconductivity: Vortex Dynamics, Vortex Phases, Pinning
TT 33.9: Talk
Friday, March 31, 2006, 12:15–12:30, HSZ 304
How the Flux Line Lattice in the Anisotropic High-Tc Superconductor Bi2Sr2CaCu2O8+δ Melts: A Magnetic Force Microscopy study — •Alexander Schwarz1, Marcus Liebmann2, Ung Hwan Pi1, and Roland Wiesendanger1 — 1University of Hamburg, IAP, Jungiusstr. 11, 20355 Hamburg — 2Present Address: RWTH Aachen, Department of Physics, 52056 Aachen
The behavior of a trigonal flux line lattice corresponding to a flux density of about 3.5 mT was investigated in a Bi2Sr2CaCu2O8+δ single crystal upon increasing the temperature stepwise from 5.1 K towards Tc. In this highly anisotropic material flux lines consist of relative weakly bound pancake vortices confined to the copper oxide planes. Magnetic force microscopy images recorded with single flux line resolution revealed a temperature dependence of the regularity of the long-range order and the apparent flux-line size. Both observations can be explained by the interplay between the temperature dependence of the London penetration depth, collective pinning and subsequent depinning above 30 K, thermal motion of the vortices and lateral dragging by the force sensor itself. At the highest temperature the typical flux line contrast composed of a coherent alignment of pancake vortices along the crystal c-axis disappeared. Instead, a liquid-like behavior of individual pancakes can be observed.