Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 31: Supraleitung: Vortexdynamik, Vortexphasen, Pinning

TT 31.4: Vortrag

Freitag, 12. März 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 T_C, 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).