Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 57: Superconductivity: Properties and Electronic Structure

TT 57.8: Talk

Thursday, April 4, 2019, 17:00–17:15, H7

Spatial modulation of the superconducting order parameter: A microscopic study of the FFLO state in an all-organic superconductor — •Sebastian Molatta^1,2, H. H. Wang³, G. Koutroulakis³, J. A. Schlueter⁴, J. Wosnitza^1,2, S. E. Brown³, and H. Kühne¹ — ¹Hochfeld-Magnetlabor Dresden (HLD-EMFL), Dresden, Germany — ²Institut für Festkörper und Materialphysik, TU Dresden, Germany — ³Department of Physics and Astronomy, UCLA, Los Angeles, USA — ⁴Division of Materials Research, National Science Foundation, Arlington, USA

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state was theoretically predicted in 1964. A hallmark of this state is the spatial modulation of the superconducting order parameter, caused by a strong spinpopulation imbalance of a Fermi liquid. So far, experimental signatures of this superconducting state were found in only very few materials. Recently, microscopic evidence for spatially modulated superconductivity was found by nuclear magnetic resonance (NMR) spectroscopy. We report on our latest results of a comprehensive NMR study of the all-organic superconductor β″-(ET)₂SF₅CH₂CF₂SO₃, focused on the spectroscopic investigation of the spatial inhomogeneous distribution of the local spin susceptibility in the FFLO phase, with related signatures in the nuclear spin-lattice relaxation rate. The inhomogeneous broadening of the ¹³C-NMR spectra, as well as the frequencydependent distribution of spin-lattice relaxation times is consistent with a one-dimensional sinusoidally modulated superconducting order parameter in the FFLO state.