Appearance of superconductivity at the vacancy order-disorder boundary in KxFe2-ySe2

Chunruo Duan, Junjie Yang, Yang Ren, Sean M. Thomas, Despina Louca

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The role of phase separation and the effect of Fe-vacancy ordering in the emergence of superconductivity in alkali metal doped iron selenides AxFe2-ySe2 (A = K, Rb, Cs) is explored. High energy x-ray diffraction and Monte Carlo simulation were used to investigate the crystal structure of quenched superconducting (SC) and as-grown nonsuperconducting (NSC) KxFe2-ySe2 single crystals. The coexistence of superlattice structures with the in-plane 2×2 K-vacancy ordering and the 5×5 Fe-vacancy ordering were observed in both the SC and NSC crystals alongside the I4/mmm Fe-vacancy-free phase. Moreover, in the SC crystals, an Fe-vacancy-disordered phase is additionally proposed to be present. Monte Carlo simulations suggest that it appears at the boundary between the I4/mmm vacancy-free phase and the I4/m vacancy-ordered phases (5×5). The vacancy-disordered phase is nonmagnetic and is most likely the host of superconductivity.

Original languageEnglish (US)
Article number184502
JournalPhysical Review B
Issue number18
StatePublished - May 14 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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