spin transport and spin filtering in superconductor nanostructures
Final Report Abstract
Superconducting spintronics aims at using the spin degree of freedom to implement electronic functionality in superconducting-ferromagnet hybrid structures. This may involve both triplet Cooper pairs or spin-polarized quasiparticles. In this project, we have focused on nonequilibrium quasiparticles in high-field superconductors, which are characterized by a spin splitting of the density of states. We have performed the first proof-of-principle experiment to demonstrate spin-dependent thermoelectric effects in superconductor-ferromagnet tunnel junctions. These thermoelectric effects are the consequence of coupled spin and heat transport in high-field superconductors, and yield very large Seebeck coefficients, on the order of 100 µV/K. We have also shown that the thermoelectric effects can be further enhanced by the proximity effect with a magnetic insulator. In addition, we have investigated non-local thermoelectric effects, which are caused by thermal injection of quasiparticles into high-field superconductors and help to elucidate the mechanism of spin transport. Possible applications of these effects are highly sensitive local electron thermometers, particle detectors and efficient Peltier microrefrigerators.
Publications
- Nonlinear thermoelectric effects in highfield superconductor-ferromagnet tunnel junctions, Beilstein J. Nanotechnol. 7, 1579 (2016)
S. Kolenda, P. Machon, D. Beckmann, and W. Belzig
(See online at https://doi.org/10.3762/bjnano.7.152) - Observation of Thermoelectric Currents in High-Field Superconductor-Ferromagnet Tunnel Junctions, Phys. Rev. Lett. 116, 097001 (2016)
S. Kolenda, M. J. Wolf, and D. Beckmann
(See online at https://doi.org/10.1103/PhysRevLett.116.097001) - Spin manipulation in nanoscale superconductors, J. Phys.: Condens. Matter 28, 163001 (2016)
D. Beckmann
(See online at https://doi.org/10.1088/0953-8984/28/16/163001) - Thermoelectric effects in superconductorferromagnet tunnel junctions on europium sulfide, Phys. Rev. B 95, 224505 (2017)
S. Kolenda, C. Sürgers, G. Fischer, and D. Beckmann
(See online at https://doi.org/10.1103/PhysRevB.95.224505) - Yu-Shiba-Rusinov bands in superconductors in contact with a magnetic insulator, J. Magn. Magn. Mater. 459, 276 (2018)
W. Belzig and D. Beckmann
(See online at https://doi.org/10.1016/j.jmmm.2017.10.062)
