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TT: Fachverband Tiefe Temperaturen
TT 76: Superconductivity: Tunnelling and Josephson Junctions II
TT 76.2: Talk
Thursday, March 21, 2024, 15:15–15:30, H 3010
Magnetization dynamics and Peierls instability in topologicalJosephson structures — •Adrian Reich1, Erez Berg2, Jörg Schmalian1,3, and Alexander Shnirman1,3 — 1Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany — 2Department of Condensed Matter Physics, Weizmann Insitute of Science, Rehovot 76100, Israel — 3Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
We study a long topological Josephson junction with a ferromagnetic strip between two superconductors. The low-energy theory exhibits a nonlocal in time and space interaction between chiral Majorana fermions, mediated by the magnonic excitations in the ferromagnet. We show that sufficiently strong and long-ranged interactions may induce a Z2-symmetry breaking, leading to a tilting of the magnetization and the opening of a fermionic gap, analogous to the Peierls instability in the commensurate Fröhlich model. Within a Gaussian fluctuation analysis, we estimate critical values for the temporal and spatial nonlocality of the interaction, beyond which the symmetry breaking is stable at zero temperature. We compare these results with a renormalization group analysis of closely related models and conclude that nonlocality, i.e., the stiffness of the magnetization in space and time, stabilizes the symmetry breaking. In the stabilized regime, we expect the current-phase relation to exhibit an experimentally accessible discontinuous jump. At nonzero temperatures, the long-range order is destroyed by solitons, which in our case carry each a Majorana zero mode.
Keywords: Topological Josephson junction; Majorana modes; One-dimensional; Fluctuation analysis