spin transport and spin filtering in superconductor nanostructures

• Applicant: Professor Dr. Detlef Beckmann
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257644405

• Final Report Year: 2018

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)
  Kolenda, Stefan; Machon, Peter; Beckmann, Detlef & Belzig, Wolfgang
  
• Observation of Thermoelectric Currents in High-Field Superconductor-Ferromagnet Tunnel Junctions, Phys. Rev. Lett. 116, 097001 (2016)
  Kolenda, S.; Wolf, M. J. & Beckmann, D.
  
• Spin manipulation in nanoscale superconductors, J. Phys.: Condens. Matter 28, 163001 (2016)
  Beckmann, D.
  
• Thermoelectric effects in superconductorferromagnet tunnel junctions on europium sulfide, Phys. Rev. B 95, 224505 (2017)
  Kolenda, S.; Sürgers, C.; Fischer, G. & Beckmann, D.
  
• Yu-Shiba-Rusinov bands in superconductors in contact with a magnetic insulator, J. Magn. Magn. Mater. 459, 276 (2018)
  Belzig, Wolfgang & Beckmann, Detlef