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TT: Fachverband Tiefe Temperaturen
TT 85: Superconductivity: Yu-Shiba-Rusinov and Andreev Physics
TT 85.6: Vortrag
Donnerstag, 12. März 2026, 16:30–16:45, CHE/0089
Emergence of new zero modes bound to vortices in extended topological Josephson junctions — •Adrian Reich1, Kiryl Piasotski1,2, and Alexander Shnirman1,2 — 1Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany — 2Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
We theoretically study planar Josephson junctions formed on the surface of a three-dimensional topological insulator (Fu-Kane proposal) and examine the experimentally relevant parameter regimes in which the effective velocity of the emergent one-dimensional Majorana modes approaches zero. We show that the frequently employed Fu-Kane effective theory breaks down in this case. As parameters like the chemical potential or the width of the junction are tuned, instances of vanishing effective velocity mark the emergence of additional ``Dirac cones'' at zero energy and finite momentum. If the junction is subjected to an external magnetic field, Josephson vortices may then bind a number of zero modes in addition to the topological Majorana mode. The additional zero modes are ``symmetry-protected'' and can be lifted by a broken mirror symmetry (which is to be expected in realistic scenarios) as well as by an in-plane magnetization (or Zeeman field). We note that the ensuing presence of additional low-energy Andreev states can significantly contribute to measured quantities like the Josephson current or microwave absorption spectra.
Keywords: Topological Josephson junction; Majorana mode