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TT: Fachverband Tiefe Temperaturen

TT 61: Topology – Poster

TT 61.13: Poster

Mittwoch, 11. März 2026, 15:00–17:00, P4

The influence of fluctuations on the microwave response of multiterminal topological Josephson junctions — •Gleb Seleznev and Wolfgang Belzig — Universität Konstanz, 78457 Konstanz, Germany

In recent years, it has been demonstrated that multiterminal Josephson junctions (MTJJs) can realize topological states of matter in synthetic dimensions defined by the superconducting phases. In this setting, topology is hosted by Weyl singularities in the spectrum of Andreev bound states (ABS) and is characterized by a nontrivial Chern number, which manifests itself in a quantized transconductance between two superconducting leads. Moreover, the Chern number leaves signatures in the dissipative part of the microwave response function, and can therefore be directly extracted using microwave spectroscopy.

In realistic experimental conditions, however, various types of fluctuations may obscure the observation of these topological properties. In this work, we investigate the role of thermal fluctuations and finite broadening of the ABS, which have a dominant effect in the large-gap limit, on the microwave response of MTJJs. We focus especially on the vicinity of the Weyl points, where the system is most sensitive to external perturbations. As a result, we demonstrate that the redefined Chern number is reduced, while other topological signatures become smeared by fluctuations.

Keywords: Multiterminal Josephson junctions; Topology; Microwave response; Fluctuatuions