Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 26: Superconductivity: Tunnelling and Josephson Junctions
TT 26.9: Vortrag
Donnerstag, 8. September 2022, 11:45–12:00, H10
Josephson effect through two superconducting magnetic impurity states — •Fabian Ziesel1, Ciprian Padurariu1, Björn Kubala1,2, and Joachim Ankerhold1 — 1ICQ and IQST, Ulm University, Germany — 2Institute of Quantum Technologies, German Aerospace Center (DLR), Ulm, Germany
A mK-STM functionalized with a magnetic impurity at the tip can probe a sample with a second impurity, thus realizing tunneling between Yu-Shiba-Rusinov (YSR) states [1]. We study the Josephson effect in such a system as a sensitive probe of the magnetic orientation of the impurities. Using Keldysh Green’s functions, we show that the subgap bound states are spin-polarized and give rise to a spin polarized Josephson current. At low transmission, the YSR states of the impurities hybridize weakly, whereas at large transmission, the bound states are strongly phase-dependent, resembling spin split Andreev bound states [2]. The spin structure of the current becomes strongly phase-dependent. For aligned or anti-aligned magnetic impurities, we show that an unusual quantum phase transition emerges. While such a Josephson current can be used as a sensitive spin probe, we find that it is accompanied by significant feedback in the form of a Josephson spin torque acting to align/anti-align the impurities.
[1] H. Huang et al., Nat. Phys. 16, 1227 (2020)
[2] B. Bujnowski et al., EPL 115, 67001 (2016)