Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 84: Focus Session: Nanoscopic Superconducting Heterostructures
TT 84.4: Invited Talk
Thursday, March 19, 2015, 11:15–11:45, H 0104
Thermoelectric Effects and Spin Injection into Superconductors with Exchange Field — •Tero Heikkilä1, Mihail Silaev2,3, Pauli Virtanen2, Francesco Giazotto4, Asier Ozaeta5, and Sebastian Bergeret5 — 1Dept Phys, Univ Jyväskylä, Finland — 2O.V. Lounasmaa Lab, Aalto Univ, Finland — 3Dept Theor Physics, KTH, Stockholm, Sweden — 4NEST CNR-INFM and SNS Pisa, Italy — 5CFM-CSIC and DIPC, San Sebastian, Spain
When a thin superconducting film is exposed to a longitudinal magnetic field or is in proximity to a ferromagnet, an exchange field separating the spin bands emerges in it. For low enough exchange fields superconductivity survives, but its response to external driving is strongly modified. In my talk I will show how at linear response such systems exhibit very strong thermoelectric response with an almost ideal efficiency. For strong driving, this effect creates a spin accumulation that can only relax via thermalization, and therefore at low temperatures has a very long range. Therefore our work explains recent observations of the long-range spin accumulation in spin-split superconductors. When injecting spin from injectors with non-collinear magnetization compared to the exchange field, the spins start to rotate around the latter. I will describe how superconductivity modifies this spin Hanle effect so that the resulting nonlocal magnetoresistance depends on the details of spin relaxation, therefore allowing for probing them.