Dresden 2017 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 70: Superconductivity: Fe-based Superconductors - Theory
TT 70.6: Vortrag
Donnerstag, 23. März 2017, 16:45–17:00, HSZ 103
Superconducting fluctuations with small Fermi energies: the case of FeSe — •Pavel A. Volkov, Ilya Eremin, and Konstantin B. Efetov — Theoretische Physik III, Ruhr-Universität Bochum, D-44780 Bochum, Germany
Recent experiments imply the presence of strong superconducting fluctuations above Tc in FeSe. It has been suggested that the observed effects could be due to the presence of a band with an anomalously small Fermi energy εF∼Δ. We report theoretical analysis of superconducting fluctuations in a two-band model with one of the bands having small εF. While close to Tc the system is described by a conventional Ginzburg-Landau theory (unless an accidental degeneracy between superconducting channels is present), the microscopic expressions for the coefficients differ from the ones obtained in the usual BCS (εF≫Δ) theory. We also present analytical expressions for fluctuation effects valid at elevated temperatures. On the basis of our results, we discuss the possible relevance of the BCS-BEC crossover to the phenomena observed in FeSe.