Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 11: Superconductivity: Poster
TT 11.35: Poster
Monday, March 17, 2025, 15:00–18:00, P4
Gate tunable superconductivity in Al/STO hybrid structures — •Jay Schmidt, Simon Reinhardt, Matthias Kronseder, Nicola Paradiso, and Christoph Strunk — Deptartment of Exp. and Appl. Physics, University of Regensburg, Germany
We present a systematic study on the gate-tunable superconducting properties of Al thin films epitaxially deposited on STO substrates. As a quantum paraelectric, STO exhibits an exceptionally high ε ≈ 7000, enabling substantial charge modulation at the Al/STO interface. Metal deposition on STO induces oxygen vacancy formation within the substrate, contributing double electron donors that create an interface 2DEG. Based on measurements of the Hall-effect we extract charge carrier densities in the Al/STO system that are comparable to those in pristine Al films and significantly surpass those observed in LAO/STO 2DEGs. This finding indicates that charge transport is predominantly mediated by Al carriers. TC(n) and BC(T,n) exhibit strong tunability under an applied gate voltage with variations up to 15% and 50%, respectively. Notably, the observed TC values (≈ 0.92 - 1.06 K) are lower than those of pristine Al thin films (≈ 1.4 K) but exceed those of STO, suggesting a bilayer system of superconductors with distinct gap energies coupled through proximity effects. We further investigate the superfluid stiffness, which turns out to be also highly gate-tunable with variations up to 15%. These results underline the potential of Al/STO heterostructures as a versatile platform for studying tunable superconducting phenomena.
Keywords: STO; strontium titanate; gate-tunable