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TT: Fachverband Tiefe Temperaturen
TT 47: Superconductivity: Properties and Electronic Structure 2
TT 47.8: Vortrag
Mittwoch, 22. März 2017, 17:15–17:30, HSZ 103
Microwave spectroscopy on superconducting Nb:SrTiO3 at mK temperatures — •Markus Thiemann1, Manfred Beutel1, Evangelos Fillis-Tsirakis2, Hans Boschker2, Jochen Mannhart2, Martin Dressel1, and Marc Scheffler1 — 11. Physikalisches Institut, Universität Stuttgart — 2Max Planck Institute for Solid State Research, Stuttgart
Niobium-doped SrTiO3 (Nb:STO) is a superconductor, exhibiting the lowest charge carrier density among all superconductors. It shows a dome in the transition temperature as a function of doping concentration with a maximum Tc≈ 0.4 K. Early tunneling experiments as well as more recent quantum oscillation measurements suggested Nb:STO being a multiband superconductor. Since the low intrinsic energy scales of the system are within the GHz range, microwave spectroscopy is the adequate contactless technique to reveal the intrinsic electronic properties of this system.
We performed microwave measurements on Nb:STO across the superconducting dome, using superconducting stripline resonators. We were able to determine the complex optical conductivity covering a temperature and frequency range of 70-500 mK and 1-20 GHz. From the complex conductivity we determined the temperature dependence of the superfluid density and superconducting energy gap. Both, as well as the frequency dependence of the complex conductivity can be described well with a single band BCS-model contradicting the multiband hypothesis.