Enhanced superconducting transition temperature in hyper-interlayer-expanded FeSe despite the suppressed electronic nematic order and spin fluctuations

Matevž Majcen Hrovat, Peter Jeglič, Martin Klanjšek, Takehiro Hatakeda, Takashi Noji, Yoichi Tanabe, Takahiro Urata, Khuong K. Huynh, Yoji Koike, Katsumi Tanigaki, Denis Arčon

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10 Citations (Scopus)

Abstract

The superconducting critical temperature, Tc, of FeSe can be dramatically enhanced by intercalation of a molecular spacer layer. Here we report on a Se77,Li7, and H1 nuclear magnetic resonance (NMR) study of the powdered hyper-interlayer-expanded Lix(C2H8N2)yFe2-zSe2 with a nearly optimal Tc=45 K. The absence of any shift in the Li7 and H1 NMR spectra indicates a complete decoupling of interlayer units from the conduction electrons in FeSe layers, whereas nearly temperature-independent Li7 and H1 spin-lattice relaxation rates are consistent with the non-negligible concentration of Fe impurities present in the insulating interlayer space. On the other hand, the strong temperature dependence of Se77 NMR shift and spin-lattice relaxation rate, 1/77T1, is attributed to the holelike bands close to the Fermi energy. 1/77T1 shows no additional anisotropy that would account for the onset of electronic nematic order down to Tc. Similarly, no enhancement in 1/77T1 due to the spin fluctuations could be found in the normal state. Yet, a characteristic power-law dependence 1/77T1T4.5 still complies with the Cooper pairing mediated by spin fluctuations.

Original languageEnglish
Article number094513
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume92
Issue number9
DOIs
Publication statusPublished - 2015 Sep 23

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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