NMR investigations toward understanding the variety of ground states in iron-based superconductors

S. Nishioka, T. Kouchi, F. Sakano, M. Yashima, H. Mukuda, M. Yogi, K. Yamaura, E. Takayama-Muromachi, S. Miyasaka, S. Tajima, H. Eisaki, A. Iyo, M. Kodani, T. Kakuto, J. H. Lee, T. Kambe

Research output: Contribution to journalConference articlepeer-review

Abstract

We report NMR experiments on heavily electron-doped Fe-based superconductor in comparison with the results on the parent Fe-based compounds. The typical parent Fe-based compound LaFe(As1-x′P x′)O exhibits the re-emergent antiferromagnetic (AFM) order at x′ ∼ 0.6 (AFM2) separated from the parent AFM order at x′ =0 (AFM1). Systematic 31P-NMR study on [Sr4Sc2O6]Fe2(As1-x P x )2 (SrSc42622), which has local lattice parameters of iron-pnictogen (FePn) layer similar to the series of LaFe(As1-x′/P x′)O, also revealed that the presence of AFM1 order is universal for most of parent Fe-based compounds. In contrast, the static AFM2 order was absent in this series, however, the dynamical low-energy AFM spin fluctuations are enhanced at around x ∼ 0.8, indicating that the onset of the static AFM2 is quite sensitive to the local lattice parameters of FePn layer. In order to elucidate the further universality and diversity, we have carried out 77Se-NMR measurement on Li x (NH3)yFe2-δ Se2 (Tc = 44 K) in heavily electron-doped regime. Although the spin fluctuations at low energies does not significantly develops upon cooling, the moderate spin fluctuations were extracted at high temperatures from comparison of the temperature (T) dependences of Knight shift and nuclear relaxation rate (1/T 1 T). We discuss the universality and diversity of the relationship between the Tc and the characteristics of the spin fluctuations in the Fe-based compounds from a microscopic point of the NMR measurements.

Original languageEnglish
Article number012008
JournalJournal of Physics: Conference Series
Volume1975
Issue number1
DOIs
Publication statusPublished - Jul 30 2021
Event33rd International Symposium on Superconductivity, ISS 2020 - Tsukuba, Japan
Duration: Dec 1 2020Dec 3 2020

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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