Cr/Fe and Pt/Co spin-mixer interfaces for spin-aligned triplet Cooper pair creation
Lead Research Organisation:
University of Cambridge
Department Name: Materials Science & Metallurgy
Abstract
Interfaces between superconductors and ferromagnets host rich physical phenomena which may find applications in low-energy computing. This is the aim of the emerging field of superconducting spintronics.
This work focuses on the fabrication of nanopillar Josephson junctions which include a ferromagnetic layer and a spin-mixer in order to investigate the generation of a long-range triplet component (LRTC) of the supercurrent. A spin-glass is predicted to arise at a Cr/Fe interface [1], which provides the magnetic inhomogeneity required to generate a LRTC. It has recently been proposed that spin-orbit coupling (SOC) may substitute the role of the magnetic inhomogeneity in interconverting the triplet states [2,3]; to investigate this we fabricate devices with Pt/Co interfaces. The SOC arises from the high atomic number of Pt and broken inversion symmetry at its interfaces, and is of pure Rashba type. Furthermore, it has been shown experimentally that interfacing a superconductor with a large SOC material enhances spin transport through the superconductor [4]; hence the combination of Fe/Cr based devices with an additional thin Pt layer is explored.
[1] Robinson, J. W. A., Banerjee, N., & Blamire, M. G. 104505, 1-4 (2014).
[2] Bergeret, F. S., & Tokatly, I. V. Phys. Rev. B 89(13), 1-13 (2014).
[3] Jacobsen, S., Kulagina, I., & Linder, J. Sci. Rep. 6:23926 (2015).
[4] Jeon, K.-R. et al. Nat. Mater. 17, 499 (2018).
This work focuses on the fabrication of nanopillar Josephson junctions which include a ferromagnetic layer and a spin-mixer in order to investigate the generation of a long-range triplet component (LRTC) of the supercurrent. A spin-glass is predicted to arise at a Cr/Fe interface [1], which provides the magnetic inhomogeneity required to generate a LRTC. It has recently been proposed that spin-orbit coupling (SOC) may substitute the role of the magnetic inhomogeneity in interconverting the triplet states [2,3]; to investigate this we fabricate devices with Pt/Co interfaces. The SOC arises from the high atomic number of Pt and broken inversion symmetry at its interfaces, and is of pure Rashba type. Furthermore, it has been shown experimentally that interfacing a superconductor with a large SOC material enhances spin transport through the superconductor [4]; hence the combination of Fe/Cr based devices with an additional thin Pt layer is explored.
[1] Robinson, J. W. A., Banerjee, N., & Blamire, M. G. 104505, 1-4 (2014).
[2] Bergeret, F. S., & Tokatly, I. V. Phys. Rev. B 89(13), 1-13 (2014).
[3] Jacobsen, S., Kulagina, I., & Linder, J. Sci. Rep. 6:23926 (2015).
[4] Jeon, K.-R. et al. Nat. Mater. 17, 499 (2018).
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509620/1 | 01/10/2016 | 30/09/2022 | |||
| 1791213 | Studentship | EP/N509620/1 | 01/10/2016 | 31/03/2020 | James Devine-Stoneman |
| Description | The interplay of superconductivity and magnetism opens the possibility of controlling spin in superconductors, which may be useful in logic and memory for low-energy computing. This work focused on two unsolved questions: 1. Can the strong spin-orbit coupling of Pt be used to generate spin currents in a superconducting device (Josephson junction)? 2. If a spin current is generated in a superconducting device, what happens to it when it meets another intermediary superconductor with conventional opposite-spin Cooper pairs? The answers at this stage appear to be: 1. This does not seem to be a promising way to generate spin currents. 2. Spin-currents decay rapidly when they enter a conventional intermediary superconductor (to be reported in a forthcoming publication). These results are important to the future design of devices for superconducting spintronics. |
| Exploitation Route | Currently, it is only of interest to the applied superconductivity research community. However, if the field yields promising results for proof-of-concept devices, it will progress to higher-level computing logic and memory applications which may be of commercial interest. |
| Sectors | Electronics |