Superconductivity of highly spin-polarized electrons in FeSe probed by Se77 NMR

A number of recent experiments indicate that the iron-chalcogenide FeSe provides the long-sought possibility to study bulk superconductivity in the cross-over regime between the weakly coupled Bardeen--Cooper--Schrieffer (BCS) pairing and the strongly coupled Bose--Einstein condensation (BEC). We report on ^{77}e nuclear magnetic resonance experiments of FeSe, focused on the superconducting phase for strong magnetic fields applied along the...