Extremely long-range, high-temperature Josephson coupling across a half-metallic ferromagnet

• Published in: Nature materials Vol. 21; no. 2; pp. 188 - 194
• Main Authors: Sanchez-Manzano, D., Mesoraca, S., Cuellar, F. A., Cabero, M., Rouco, V., Orfila, G., Palermo, X., Balan, A., Marcano, L., Sander, A., Rocci, M., Garcia-Barriocanal, J., Gallego, F., Tornos, J., Rivera, A., Mompean, F., Garcia-Hernandez, M., Gonzalez-Calbet, J. M., Leon, C., Valencia, S., Feuillet-Palma, C., Bergeal, N., Buzdin, A. I., Lesueur, J., Villegas, Javier E., Santamaria, J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.02.2022; Nature Publishing Group
• Subjects: 142/126; 639/301/119/1003; 639/766/119/1003; Biomaterials; Chemistry and Materials Science; Condensed Matter Physics; Coupling; Critical current (superconductivity); Experiments; Ferromagnetism; Flux quantization; High temperature; Interfaces; Josephson effect; Locking; Magnetic flux; Manganites; Materials Science; Nanotechnology; Optical and Electronic Materials; Physics; Polarization (spin alignment); Quantum computing; Spintronics; Superconductivity; Superconductors; Temperature; Wire; YBCO superconductors
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/s41563-021-01162-5

The Josephson effect results from the coupling of two superconductors across a spacer such as an insulator, a normal metal or a ferromagnet to yield a phase coherent quantum state. However, in junctions with ferromagnetic spacers, very long-range Josephson effects have remained elusive. Here we demonstrate extremely long-range (micrometric) high-temperature (tens of kelvins) Josephson coupling across the half-metallic manganite La 0.7 Sr 0.3 MnO 3 combined with the superconducting cuprate YBa 2 Cu 3 O 7 . These planar junctions, in addition to large critical currents, display the hallmarks of Josephson physics, such as critical current oscillations driven by magnetic flux quantization and quantum phase locking effects under microwave excitation (Shapiro steps). The latter display an anomalous doubling of the Josephson frequency predicted by several theories. In addition to its fundamental interest, the marriage between high-temperature, dissipationless quantum coherent transport and full spin polarization brings opportunities for the practical realization of superconducting spintronics, and opens new perspectives for quantum computing. Josephson coupling over micrometres and at tens of kelvins is demonstrated across the half-metallic manganite La 0.7 Sr 0.3 MnO 3 combined with the superconducting cuprate YBa 2 Cu 3 O 7 .