Appearance of superconductivity at the vacancy order-disorder boundary in KxFe2−ySe2
Chunruo Duan, Junjie Yang, Yang Ren, Sean M. Thomas, Despina Louca
DOI 10.1103/PhysRevB.97.184502 · Physical Review B
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Abstract
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.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| KxFe2-ySe2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 29 | Pressure not reported | onset |
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