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TT: Fachverband Tiefe Temperaturen

TT 9: Quantum Dots, Quantum Wires, Point Contacts

TT 9.3: Talk

Monday, March 12, 2018, 10:15–10:30, HFT-FT 101

Odd-frequency superconductivity revealed by thermopower — Sun-Yong Hwang¹, Pablo Burset², and •Björn Sothmann¹ — ¹Theoretische Physik, Universität Duisburg-Essen and CENIDE, D-47048 Duisburg, Germany — ²Department of Applied Physics, Aalto University, FIN-00076 Aalto, Finland

Conventional superconductivity is well-explained in the framework of BCS theory by the formation of spin-singlet Cooper pairs. However, other exotic types of superconductivity involving, e.g., spin-triplet pairs exist as well. In general, superconducting correlations can be characterized by a nonvanishing pair amplitude which has a definite symmetry in spin, momentum and time or frequency. While the spin and momentum symmetry have been probed experimentally for different classes of superconductivity, the odd-frequency nature of certain superconducting correlations has so far been probed only indirectly. Here, we propose the thermopower as an unambiguous way to assess odd-frequency superconductivity. This is possible since the thermoelectric coefficient given by Andreev-like processes is only finite in the presence of odd-frequency superconductivity. We illustrate our general findings with a simple example of a superconductor-quantum dot-ferromagnet hybrid.