Breaking of four-fold rotational symmetry driven by stripe-type magnetism in semiconducting KFe<sub>0.8</sub>Ag<sub>1.2</sub>Te<sub>2</sub>

ORAL

Abstract

Superconductivity in the iron pnictides and chalcogenides emerges in the vicinity of an electronic nematic state, whose driving force remains controversial. We use X-ray and neutron scattering to study the semiconducting alkaline metal iron chalcogenide KFe0.8Ag1.2Te2, that is structurally analogous to the prototypical iron pnictide BaFe2As2. We find that KFe0.8Ag1.2Te2 realizes isolated 2x2 Fe blocks, separated by nonmagnetic Ag atoms. Long-range magnetic order sets in below TN = 35 K, with magnetic moments within each Fe block ordering into a stripe-type configuration. A structural transition that breaks four-fold rotational symmetry of the lattice accompanies the magnetic transition, resulting in different lattice spacings along the two orthogonal Fe-Fe bond directions. This difference in lattice spacings is similar to that in BaFe2As2 in magnitude, and like BaFe2As2, the lattice spacing is longer along the antiferromagnetically aligned Fe-Fe direction. Since KFe0.8Ag1.2Te2 is a semiconductor, local-moment magnetism is likely responsible for driving the breaking of four-fold rotational symmetry, and similar magnetic interactions may play an important role in the superconducting alkaline metal iron chalcogenides.

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Presenters

  • Yu Song

    • Physics, University of California, Berkeley
    • Rice University
    • University of California, Berkeley

Authors

  • Yu Song

    • Physics, University of California, Berkeley
    • Rice University
    • University of California, Berkeley

  • Huibo Cao

    • Neutron Scattering Division, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory
    • Quantum Condensed Matter Division, Oak Ridge National Laboratory

  • Bryan C. Chakoumakos

    • Oak Ridge National Laboratory

  • Yang Zhao

    • NIST Center for Neutron Research, National Institute of Standards and Technology
    • NCNR, NIST

  • Aifeng Wang

    • Brookhaven National Laboratory
    • CMPMSD, Brookhaven National Laboratory

  • Hechang Lei

    • Physics Department, Renmin University of China
    • Brookhaven National Laboratory
    • Renmin University of China
    • Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory

  • Cedomir Petrovic

    • CMPMS, Brookhaven National Laboratory
    • Brookhaven National Laboratory
    • CMPMSD, Brookhaven National Laboratory
    • Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory

  • Robert J Birgeneau

    • University of California, Berkeley
    • Physics, University of California, Berkeley
    • Univ. of California, Berkeley
    • Physics, University of California Berkeley