Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 25: Superconductivity: Supercurrent Diode Effect

TT 25.6: Talk

Wednesday, March 19, 2025, 10:45–11:00, H32

Spin and Charge Josephson Diode Effect in Diffusive Superconductor-Ferromagnet Heterostructures — •Niklas L. Schulz, Danilo Nikolić, and Matthias Eschrig — Institut für Physik, Universität Greifswald, Felix-Hausdorff-Strasse 6, 17489 Greifswald, Germany

Long-range equal-spin triplet supercurrents in the presence of a nontrivial spin texture are of fundamental importance for applications of superconducting spintronics [1]. In this work we investigate quantum geometric phases in a Josephson trilayer consisting of a strongly spin-polarized ferromagnet connected to BCS superconductors by ferromagnetic insulating barriers. For non-coplanar spin textures of the device, spin-geometric phases arise, which enter the current-phase relation additionally to the superconducting phase difference [2]. In general, such spin-geometric phases are induced by gauge fields entering the transport equation [3] and in the considered case these are caused by spin-dependent U(1) gauge fields. The resulting current-phase relation in such devices allows for the observation of a Josephson diode effect in the charge current for symmetric systems and a diode effect in the spin current for asymmetric configurations. In certain cases, the device also allows to switch between fully spin-polarized supercurrents across the ferromagnet by reversing the Josephson phase.

[1] M. Eschrig, Rep. Prog. Phys. 78, 104501 (2015)

[2] R. Grein et al., Phys. Rev. Lett. 102, 227005 (2009)

[3] I. V. Bobkova et al., Phys. Rev. B 96, 094506 (2017)

Keywords: Superconducting spintronics; Josephson diode effect; Geometric phases; Proximity effect