Dresden 2014 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity: Vortex Physics
TT 33.3: Talk
Tuesday, April 1, 2014, 10:15–10:30, HSZ 201
Spatial-dependent critical magnetic field for the suppression of superconductivity in a single Pb island with non-uniform thickness — •Augusto Leon Vanegas1, Agnieszka Stepniak1, Michael Caminale1, Hirofumi Oka1, Dirk Sander1, and Jürgen Kirschner1,2 — 1Max-Planck-Institute of Microstructure Physics, Halle, Germany — 2Martin Luther University Halle-Wittenberg
We have studied the superconducting properties of Pb islands of 7−10 layers thickness and sizes of 1600−10000 nm2 on Pb/Ag/Si(111) with a 3He cooled scanning tunnelling microscope (3He-STM) with a vector magnetic field. Spatially resolved scanning tunnelling spectroscopy(STS) at 1.8 K shows a uniform superconducting gap across the islands at 0 T. We have measured the differential conductance at zero bias (ZBC) across several islands with varying the magnetic field perpendicular to the island surface. We identify the vortex formation field (HC1) for islands larger than 5000 nm2 and the critical field for suppressing superconductivity (HC2) in the islands. Below HC1 the islands remain superconducting with small spatial variations of the ZBC from the centre to the edge of the island, which we ascribe to Meissner screening currents along the island perimeter. Between HC1 and HC2 spectroscopy indicates the formation of a single vortex, with normal conductance at its centre. We observe that for islands with a non-uniform height, HC2 varies across the island. The thickest part of the island remains superconducting at higher magnetic field.