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arXiv · 1711.11538

Spin-flip Enhanced Thermoelectricity in Superconductor-Ferromagnet Bilayers

A. Rezaei·A. Kamra·P. Machon·W. Belzig
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Abstract

We study the effects of spin-splitting and spin-flip scattering in a superconductor (S) on the thermoelectric properties of a tunneling contact to a metallic ferromagnet (F) using the Green's function method. A giant thermopower has been theoretically predicted and experimentally observed in such structures. This is attributed to the spin-dependent particle-hole asymmetry in the tunneling density of states in the S/F heterostructure. Here, we evaluate the S density of states and thermopower for a range of temperatures, Zeeman-splitting, and spin-flip scattering. In contrast to the naive expectation based on the negative effect of spin-flip scattering on Cooper pairing, we find that the spin-flip scattering strongly enhances the thermoelectric performance of the system in the low-field and low-temperature regime. This is attributed to a complex interplay between the charge and spin conductances caused by the softening of the spin-dependent superconducting gaps. The maximal value of the thermopower exceeds $k_{B}/e$ by a factor of $\approx$ 5 and has a nonmonotonic dependence on spin-splitting and spin-flip rate.

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A. Rezaei, A. Kamra, P. Machon, W. Belzig. 2017-11-30. Spin-flip Enhanced Thermoelectricity in Superconductor-Ferromagnet Bilayers. https://doi.org/10.1088/1367-2630%2Faad2a3

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