Dresden 2020 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 55: Superconductivity: Tunnelling and Josephson Junctions

TT 55.4: Vortrag

Donnerstag, 19. März 2020, 10:30–10:45, HSZ 204

Coupling ferromagnetic insulators via quasiparticle states in a nodal superconductor — •Angelo Di Bernardo1,2, Sachio Komori2, Giorgio Livanas3, Giorgio Divitini2, Paola Gentile3, Mario Cuoco3, and Jason Robinson21Universität Konstanz, Department of Physics, Universitätsstraße 10, Konstanz, Germany — 2Universitatstrasse 10 — 3CNR-SPIN, c/o University of Salerno, I-84084 Fisciano, Salerno, Italy

The generation of parallel-aligned spin (spin-triplet) pairs of electrons at superconductor/ferromagnet (S/F) interfaces has triggered the field of superconducting spintronics –which aims at developing spintronic devices with high energy efficiency.

Even before the discovery of giant magneto resistance, which underlies spintronic spin valves, de Gennes predicted a FI/S/FI system (FI is a ferromagnetic insulator), where a variation in the critical temperature (Δ Tc) of S can be obtained by switching the FIs from parallel (P) to antiparallel (AP). In addition, if the S thickness (dS) is smaller than its coherence length (ξ), S can favour an AP coupling of the FIs.

Recently, we have investigated a fully-oxide FI/S/FI system [1], where FI is the manganite Pr0.8Ca0.2MnO3 and S is the nodal (d-wave) S YBa2Cu3O7−δ (YBCO). Here, quasiparticle states at the Fermi surface of YBCO, induce a long-ranged exchange coupling between the FIs over a dS up to 100 ξ, which is well-beyond de Gennes limit for a metallic FI/S/FI system. Such nodal exchange coupling reinforces an AP state at specific dS and results in Δ Tc values up to 2 K.

[1] A. Di Bernardo et al., Nature Mater. 18, 1194 (2019).

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