Giant thermoelectric effects in a proximity-coupled superconductor–ferromagnet device

Abstract

The usually negligibly small thermoelectric effects in superconducting heterostructures can be boosted dramatically due to the simultaneous effect of spin splitting and spin filtering. Building on an idea of our earlier work (Machon et al 2013 Phys. Rev. Lett. http://dx.doi.org/10.1103/PhysRevLett.110.047002 110 http://dx.doi.org/10.1103/PhysRevLett.110.047002 ), we propose realistic mesoscopic setups to observe thermoelectric effects in superconductor heterostructures with ferromagnetic interfaces or terminals. We focus on the Seebeck effect being a direct measure of the local thermoelectric response and find that a thermopower of the order of $\sim 250$ $\mu V\;{{K}^{-1}}$ can be achieved in a transistor-like structure. A measurement of the thermopower can furthermore be used to determine quantitatively the spin-dependent interface parameters that induce the spin splitting. For applications in nanoscale cooling we discuss the figure of merit for which we find values exceeding 1.5 for temperatures $\lesssim 1$ K.

Keywords

• thermopower
• figure of merit
• proximity effect
• quasiclassical theory
• spin-dependent boundary conditions
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