Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 32: Postersession Superconductivity: Josephson Junctions, SQUIDs, Heterostructures, Andreev Scattering, Vortex Physics, Cryodetectors, Measuring Devices, Cryotechnique
TT 32.33: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
A scanning tunneling microscope for low temperatures — •Michael Marz1,2, Gernot Goll1, and Hilbert v. Löhneysen1,2,3 — 1Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe — 2DFG-Centrum für Funktionelle Nanostrukturen der Universität Karlsruhe (TH), 76128 Karlsruhe — 3Institut für Festkörperphysik Forschungszentrum Karlsruhe, 76021 Karlsruhe
Scanning tunneling microscopy (STM) and spectroscopy (STS) are widely used to study topological and electronic properties of conducting materials. We installed a home-built STM into a dilution refrigerator, where we can reach temperatures down to 30 mK and apply magnetic fields up to 13 T. Calibration of the piezo of the scanning head was done on HOPG and NbSe2 at room temperature, on both we achieved atomic resolution. At low temperatures we imaged with atomic resolution the topography of NbSe2 as well as the flux-line lattice in small magnetic fields. The lattice constant a of the Abrikosov lattice shows the expected field dependence a∝ 1/√B. Spectroscopy clearly shows the superconducting density of states and Andreev bound states in the vortex core. The energy gap determined from a fit of the dI/dV vs. V curves reveals a distribution of the gap values probably due to the presence of the charge-density wave in NbSe2.