Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 50: German-French Focus Session: Superconducting Junctions and Quantum Circuits

TT 50.7: Vortrag

Mittwoch, 11. März 2026, 18:00–18:15, HSZ/0003

Multiterminal Josephson Junctions: non-hermiticity, topology and reflectionless modes — •David Christian Ohnmacht, Wilhelm Valentin, Weisbrich Hannes, and Belzig Wolfgang — Universität Konstanz, Konstanz, Germany

In multiterminal Josephson junctions (MTJJs), the Andreev bound state energies depend on multiple phase differences, enabling band structure engineering. MTJJs are predicted to host non-trivial topological phases and associated Weyl nodes in the synthetic Brillouin zone spanned by these superconducting phases [1]. In [2], spectroscopic measurements were performed on four-terminal Josephson junctions with phase control of all three superconducting phase differences, unveiling the presence of a tri-Andreev molecule, compatible with a topologically non-trivial model. We predict that such MTJJs, in the presence of additional normal leads, host non-trivial non-Hermitian topology, leading to spectral topology in the form of point gaps and Weyl disks [3]. Additionally, we predict that reflectionless scattering modes in MTJJs are a source of topological phase boundaries [4]. Our work provides an effective bulk boundary correspondence by demonstrating a relationship between unity transmission modes and boundaries between topologically trivial and non-trivial regions, like in quantum Hall systems.
[1] R.-P. Riwar et. al., Nature Commun. 7, 1 (2016)
[2] T. Antonelli et. al., Phys. Rev. X 15, 031066 (2025)
[3] D. C. Ohnmacht et. al., Phys. Rev. Lett. 134, 156601 (2025)
[4] D. C. Ohnmacht et. al., arXiv:2503.10874 (2025)

Keywords: Josephson junctions; Multiterminal Josephson junctions; Topology; non-Hermitian physics; non-Hermitian topology