Jason Robinson (Special Seminar)

Date(s) - May 13 2014
11:00 AM - 12:00 PM

Shasta Room, Bldg. 40, Room 361


Spin-polarized Cooper pairs and spin-selectivity in superconducting spin-valves

Jason Robinson

University of Cambridge

Spin selectivity in a ferromagnet results from a difference in the density of up- and down-spin electrons at the Fermi energy as a consequence of which the scattering rates depend on the spin orientation of the electrons. This property is utilized in spintronics to control the flow of electrons by ferromagnets in ferromagnet (F1)/normal metal (N)/ferromagnet (F2) spin valves, where F1 acts as the polarizer and F2 the analyzer or vice-versa.

The feasibility of superconducting spintronics depends on the spin sensitivity of ferromagnets to the spin of the equal-spin triplet Cooper pairs (1) which are generated superconductor(S)-ferromagnet(F) heterostructures with magnetic inhomogeneity at the S-F interface (2-5). In this talk I will first introduce the topic of singlet and triplet pair superconductor proximity effects in SF heterostructures. I will discuss recent results from our group on superconducting FSF spin-valves with holmium spin mixers at the SF interface, which demonstrate evidence of a spin selectivity of the ferromagnets to the spin of the triplet Cooper pairs (6,7). Since spin-selectivity is an indispensible requirement for the future development of spin electronics our results represent an important milestone in this field.

  1. M. Eschrig. Phys. Today 64, 43-49 (2011).
  2. J.W.A. Robinson, J.D.S. Witt, M.G. Blamire. Science 329, 59 (2010); G.B. Halász, M.G. Blamire, J.W.A. Robinson. Phys. Rev. B 84, 024517 (2011).
  3. T. Khaire, M. Khasawneh, W.P Pratt, N. Birge. Phys. Rev. Lett. 104, 137002 (2010).
  4. C. Klose et al. Phys. Rev. Lett. 108, 127002 (2012).
  5. M. Anwar, M. Veldhorst, A. Brinkman, J. Aarts. Appl. Phys. Lett. 100, 052602 (2012).
  6. N Banerjee, C Smiet, R Smits, A Ozaeta, F Bergeret, M Blamire, JWA Robinson. Nature Comm. 5, 3048 (2014).
  7. XL Wang, A Di Bernardo, N Banerjee, A Wells, FS Bergeret, MG Blamire and JWA Robinson, Phys. Rev. B. Rapid (in-press)