Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 81: Superconductivity: Properties and Electronic Structure
TT 81.13: Vortrag
Donnerstag, 3. April 2014, 12:45–13:00, HSZ 201
Position-dependent tunneling spectroscopy from a superconducting Pb island towards a normal conducting single layer — •Agnieszka Stepniak1, Augusto A. Leon Vanegas1, Michael Caminale1, Hirofumi Oka1, Dirk Sander1, and Jürgen Kirschner1,2 — 1Max-Planck-Institute of Microstructure Physics, Halle, Germany — 2Martin Luther University Halle-Wittenberg, Halle, Germany
Using scanning tunneling microscopy (STM) and spectroscopy (STS) we study the superconducting properties of Pb islands on a Ag monolayer on Si(111). We use a 3He-cooled STM with a vector magnetic field to characterize the structural and electronic properties of the Pb/Ag-Si system at the temperatures range of 0.38*4.0 K, in dependence of a magnetic field of up to 6 T along the sample normal. We find SC in Pb islands, where the transition temperature is 6 K in a 9 layer high Pb island. The interlayer of Ag suppresses superconductivity (SC) in single layer Pb surrounding the Pb islands. We exploit the spatial resolution of STM/STS to study the position dependent differential conductivity for a transition from a SC Pb island to the surrounding non-superconducting Pb layer on Ag/Si, as a function of temperature and magnetic field. The quantitative analysis of the SC gap in spectroscopy identifies an exponential decay on which SC faints into the normal-metal region with a decay length of 5+/-1 nm at 1.8 K. This length is larger at lower temperature (10 nm at 0.4 K), and smaller at higher temperature (1 nm at 4 K). A magnetic field of up to 0.5 T along the sample normal does not change the decay length.