Strong correlations between vacancy and magnetic ordering in superconducting K0.8Fe2−ySe2
J. Yang, C. Duan, Q. Huang, C. Brown, J. Neuefeind, Despina Louca
DOI 10.1103/PhysRevB.94.024503 · Physical Review B
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Abstract
The coexistence of magnetic and nonmagnetic phases in the superconducting potassium iron selenide, KxFe2−ySe2, has been intensely debated. With superconductivity proposed to appear in a stoichiometric, nonmagnetic phase with I4/mmm crystal symmetry, the proposed nonsuperconducting phase is magnetic and has a lower symmetry, I4/m. The latter consists of Fe vacancies that go through a disordered-to-ordered transition in which the partially filled Fe sites create a supercell upon ordering. We show, using neutron scattering on the optimally doped composition, K0.8Fe2−ySe2, that the absence of magnetism does not signal the presence of superconductivity. Moreover, the degree of vacancy order is coupled to the strength of the magnetic order. Superconductivity coincides with the presence of the magnetic order parameter, albeit the latter is significantly weaker than previously reported, contradicting the current understanding of this ∼30K superconductor.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| K0.8Fe2-ySe2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 31 | Pressure not reported | onset |
| Fe1-ySe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 8 | Pressure not reported | unknown |
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