Superconducting pure spin currents generated via spin-orbit coupling

Speaker: Professor Jason Robinson (Department of Materials Science, University of Cambridge)

Title: Superconducting pure spin currents generated via spin-orbit coupling

Abstract: Spin currents are fundamental to spintronics, but in the normal state large charge currents are required at device inputs in order to generate sufficiently large output spin current densities. In this talk I will review our group’s work on superconducting pure spin currents through the transfer of spin angular momentum via proximity-induced equal-spin triplet states in superconducting Nb^1,2. In agreement with recent theory^3-5 and experiments^2,6, I will show that spin-orbit coupling (SOC) in conjunction with a magnetic exchange field generates spin-polarized triplet pairs. In particular, I will demonstrate that when a perpendicularly magnetized Pt/Co/Pt spin sink is proximity-coupled to superconducting Nb, ferromagnetic spin-pumping efficiency in the superconducting state is tunable by controlling the tilt angle of the Co layer magnetization, thus increasing the degree of orthogonality between the SOC and magnetic exchange field at the Nb/Pt/(Co/Pt) interface. The results are central to the development of superconducting devices with charge and spin-degrees of freedom.

References:

1. J. Linder, J. W. A. Robinson, Nat. Phys. 11, 307–315 (2015). 

2. K.-R. Jeon et al. Nat. Mater. 17, 499–503 (2018).

3. F. S. Bergeret and I. V. Tokatly, Phys. Rev. B 89, 134517 (2014).

4. S. Jacobsen, J. Ouassou, A. Jabir, J. Linder, J. Phys. Rev. B 92, 024510 (2015).

5. X. Montiel, M. Eschrig, Phys. Rev. B 98, 104513 (2018).

6. N. Banerjee et al., Phys. Rev. B 97, 184521 (2018).