Regensburg 2004 – scientific programme
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TT: Tiefe Temperaturen
TT 31: Supraleitung: Vortexdynamik, Vortexphasen, Pinning
TT 31.4: Talk
Friday, March 12, 2004, 11:00–11:15, H20
Observation of Abrikosov Lattice Melting in Real Space by Magnetic Force Microscopy — •Alexander Schwarz, Marcus Liebmann, and Roland Wiesendanger — IAP, University of Hamburg, Hamburg, Germany
In this study, we use low temperature magnetic force microscopy to visualize the melting of a regular Abrikosov vortex lattice frozen into a Bi2Sr2CaCu2O8 single crystal by field cooling. Due to the high sensitivity and spatial resolution of our instrument (below 50 nm [1]), individual flux lines (perpendicular bound pancake vortices) are easily resolved. Upon increasing the temperature towards TC, the flux lines appear broader, because (i) the penetration depth increases, and (ii) they become more mobile within their lattice position. However, the regular hexagonal arrangement stays intact, until a certain temperature (T ≈ 50 K) is reached beyond which the contrast vanishes. Strongly pinned individual vortices can remain visible and act as scattering centers for the now unbound pancake vortices, which are in the liquid state. After recondensation, the regular hexagonal arrangement is restored, but somewhat tilted with respect to the original configuration.
[1] M. Liebmann et al., Rev. Sci. Instrum. 73, 3508 (2002).