Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 19: Topological Superconductors
TT 19.3: Vortrag
Mittwoch, 7. September 2022, 12:15–12:30, H23
Tunable 4π-periodic supercurrent in HgTe-based topological nanowires — Ralf Fischer1, Jordi Picó-Cortés2,3, •Wolfgang Himmler1, Gloria Platero2, Milena Grifoni3, Dimitry Kozlov4, Nikolay Mikhailov4, Sergey Dvoretsky4, Christoph Strunk1, and Dieter Weiss1 — 1Experimental and Applied Physics, University of Regensburg — 2Instituto de Ciencia de Materiales de Madrid — 3Institute of Theoretical Physics, University of Regensburg — 4Novosibirsk, Russia
Topological insulator nanowires in proximity to conventional superconductors have been proposed as a tunable platform to realize topological superconductivity. The tuning is done using an axial magnetic flux Φ which allows transforming the system from trivial at Φ=0 to topologically nontrivial when half a magnetic flux quantum Φ=Φ0/2 threads the cross-sectional area of the wire.
In our work, we investigate Josephson junctions based on HgTe nanowires and probe the Shapiro step spectrum. From the suppression of odd Shapiro steps, we extract the 4π- and 2π-periodic portion of the supercurrent I4π and I2π using a resistively and capacitively shunted junction model. The ratio I4π/I2π changes from a small value of few percent at Φ=0 up to a maximum at Φ=Φ0/2. The presence of I4π at Φ=0 and small magnetic fields indicate that in this regime Landau-Zener transitions cause the 4π-periodic current. By disentangling the 4π-periodic supercurrent of trivial an topological origin, our data suggest that topological 4π-periodic supercurrents dominate at axial magnetic fields above Φ0/4.