The rise of superconducting spintronics
Par Angelo Di Bernardo, University of Cambridge, St John’s College, Cambridge (UK)
Mardi 29 Janvier, 14h00, Salle des séminaires (215), 2ème étage, Bâtiment A4N
Abstract :
The interaction between materials with radically different properties can lead to the emergence of tantalising physical phenomena. A typical example of such an interaction is that occurring at a superconductor/ferromagnet (S/F) interface where unconventional – odd frequency spin-triplet – superconducting states can arise and support a net spin-polarization.
The spin-polarization stems from the fact that, in the presence of an inhomogeneous magnetisation, the Cooper pairs form in a spin-triplet state in which the electron spins are parallel with a pair wavefunction that is odd in symmetry with respect to exchange of time coordinates. After the theoretical proposition for the generation of such odd-frequency spin-triplet states in S/F systems with a magnetically inhomogeneous F, experimental evidence for them had been indirectly found via transition temperature (Tc) measurements of S/F1/F2 spin valves and supercurrent measurements in S/F/S Josephson junctions.
In this talk, I will discuss experiments that I performed demonstrating direct evidence for odd-frequency spin-triplets and other unconventional superconducting states emerging in a conventional S proximity-coupled to F or normal metals like graphene. The experiments have been performed probing the superconducting density of states of such heterostructures using low-temperature scanning tunnelling microscopy and spectroscopy and the local field profile in the Meissner state using low-energy muon spectroscopy [1-3].
The spin-polarization stems from the fact that, in the presence of an inhomogeneous magnetisation, the Cooper pairs form in a spin-triplet state in which the electron spins are parallel with a pair wavefunction that is odd in symmetry with respect to exchange of time coordinates. After the theoretical proposition for the generation of such odd-frequency spin-triplet states in S/F systems with a magnetically inhomogeneous F, experimental evidence for them had been indirectly found via transition temperature (Tc) measurements of S/F1/F2 spin valves and supercurrent measurements in S/F/S Josephson junctions.
In this talk, I will discuss experiments that I performed demonstrating direct evidence for odd-frequency spin-triplets and other unconventional superconducting states emerging in a conventional S proximity-coupled to F or normal metals like graphene. The experiments have been performed probing the superconducting density of states of such heterostructures using low-temperature scanning tunnelling microscopy and spectroscopy and the local field profile in the Meissner state using low-energy muon spectroscopy [1-3].
REFERENCES
[1] A. Di Bernardo et al., Nat. Comm. 6, 8053 (2015).
[2] A. Di Bernardo et al., Phys. Rev. X 5, 041021 (2015).
[3] A. Di Bernardo et al., Nat. Comm. 8, 14024 (2017).
[1] A. Di Bernardo et al., Nat. Comm. 6, 8053 (2015).
[2] A. Di Bernardo et al., Phys. Rev. X 5, 041021 (2015).
[3] A. Di Bernardo et al., Nat. Comm. 8, 14024 (2017).