Strong correlations between vacancy and magnetic ordering in superconducting K0.8Fe2ySe2

J. Yang, C. Duan, Q. Huang, C. Brown, J. Neuefeind, and Despina Louca
Phys. Rev. B 94, 024503 – Published 5 July 2016

Abstract

The coexistence of magnetic and nonmagnetic phases in the superconducting potassium iron selenide, KxFe2ySe2, 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, K0.8Fe2ySe2, 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.

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  • Received 16 November 2015
  • Revised 7 June 2016

DOI:https://doi.org/10.1103/PhysRevB.94.024503

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

J. Yang1, C. Duan1, Q. Huang2, C. Brown2, J. Neuefeind3, and Despina Louca1,*

  • 1University of Virginia, Charlottesville, Virginia 22904, USA
  • 2NIST Center for Neutron Research, Gaithersburg, Maryland 20899, USA
  • 3Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • *louca@virginia.edu

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Issue

Vol. 94, Iss. 2 — 1 July 2016

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