Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 25: Superconductivity: Supercurrent Diode Effect

TT 25.5: Talk

Wednesday, March 19, 2025, 10:30–10:45, H32

Spin-Resolved Josephson Diode Effect in Strongly Polarized SFS Junctions — •Danilo Nikolić, Niklas L. Schulz, and Matthias Eschrig — Institut für Physik, Universität Greifswald, Felix-Hausdorff-Strasse 6, 17489 Greifswald, Germany

We present a systematic study of equal-spin Cooper pair formation at the interface between a superconductor (S) and a helical ferromagnet (F) [1]. The theory is done in the framework of the quasiclassical Green’s function formalism [2-4]. However, assuming the large splitting between the spin bands in F, the standard quasiclassical approach cannot be applied directly and requires a modified description [5-8]. Applying this approach, we account for the long-ranged (equal-spin) Josephson current-phase relation (CPR) in an SFS weak link considering a helimagnetic state in F. Remarkably, the CPR takes a nontrivial form leading to both the anomalous and Josephson diode effects. These effects have clear physical interpretations based on the coupling between the superconducting phase and the adiabatic spin gauge field (geometric phase) induced by inhomogeneous magnetization of F.

[1] A. Spuri et al., Phys. Rev. Res. 6, L012046 (2024).

[2] G. Eilenberger, Z. Phys. 214, 195 (1968).

[3] A.I.Larkin, Yu.N.Ovchinnikov, Sov. Phys. JETP 28, 1200 (1969).

[4] A. I. Buzdin, Rev. Mod. Phys. 77, 935 (2005).

[5] M. Eschrig, Phys. Rev. B 80, 134511 (2009).

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

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

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

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