Nonlinear thermoelectric effects in high-field superconductor-ferromagnet tunnel junctions

• Main Authors: Kolenda, S, Machon, P, Beckmann, D, Belzig, W
• Format: Journal Article
• Language: English
• Published: 07-04-2016
• Subjects: Physics - Mesoscale and Nanoscale Physics; Physics - Superconductivity
• DOI: 10.48550/arxiv.1604.01940

Thermoelectric effects result from the coupling of charge and heat transport,
and can be used for thermometry, cooling and harvesting of thermal energy. The
microscopic origin of thermoelectric effects is a broken electron-hole
symmetry, which is usually quite small in metal structures, and vanishes at low
temperatures. We report on a combined experimental and theoretical
investigation of thermoelectric effects in superconductor/ferromagnet hybrid
structures. We investigate the depencence of thermoelectric currents on the
thermal excitation, as well as on the presence of a dc bias voltage across the
junction. Large thermoelectric effects are observed in
superconductor/ferromagnet and superconductor/normal-metal hybrid structures.
The spin-independent signals observed under finite voltage bias are shown to be
reciprocal to the physics of superconductor/normal-metal microrefrigerators.
The spin-dependent thermoelectric signals in the linear regime are due to the
coupling of spin and heat transport, and can be used to design more efficient
refrigerators