Dresden 2017 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 53: Poster Session: Superconductivity 1
TT 53.18: Poster
Wednesday, March 22, 2017, 15:00–19:00, P2-OG2
High field 77Se NMR on single crystalline FeSe. — •Sebastian Molatta1,2,3, Z. T. Zhang1,4, R. Sarkar2,3, P. Biswas5, T. Wolf6, H. v. Löhneysen6, J. Wosnitza1,2,3, and H. Kühne1 — 1Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Germany — 2IFP, Technical University of Dresden, Germany — 3DFG GRK 1621 — 4Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Germany — 5Paul-Scherrer-Institute, Switzerland — 6IFP, Karlsruhe Institute of Technology, Germany
FeSe is currently discussed as a superconductor in the crossover regime between the weakly coupled Bardeen-Cooper-Schrieffer (BCS) and the strongly coupled Bose-Einstein-condensate (BEC) limit. In particular, at high magnetic fields, the energies of the Zeeman interaction, superconducting gap, and the Fermi temperature are comparable in FeSe. We report recent results of the spin susceptibility and low-energy quasiparticle excitations probed by means of nuclear magnetic resonance (NMR) spectroscopy in the highly spin-polarized state close to the upper critical field of superconductivity. The superconducting state is evidenced by a reduced radio-frequency penetration depth reflected by a decreasing NMR signal intensity towards low temperatures. The spin-lattice relaxation rate points towards a field-induced change of the gap structure within the superconducting state.