Intertwined magnetic and nematic orders in semiconducting KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$

Abstract

Superconductivity in the iron pnictides emerges from metallic parent compounds exhibiting intertwined stripe-type magnetic order and nematic order, with itinerant electrons suggested to be essential for both. Here we use X-ray and neutron scattering to show that a similar intertwined state is realized in semiconducting KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$ (K${}_5$Fe${}_4$Ag${}_6$Te${}_{10}$) without itinerant electrons. We find Fe atoms in KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$ form isolated $2\times 2$ blocks, separated by nonmagnetic Ag atoms. Long-range magnetic order sets in below $T_{\mathrm{N}}\approx 35$ K, with magnetic moments within the $2\times 2$ Fe blocks ordering into the stripe-type configuration. A nematic order accompanies the magnetic transition, manifest as a structural distortion that breaks the fourfold rotational symmetry of the lattice. The nematic orders in KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$ and iron pnictide parent compounds are similar in magnitude and how they relate to the magnetic order, indicating a common origin. Since KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$ is a semiconductor without itinerant electrons, this indicates that local-moment magnetic interactions are integral to its magnetic and nematic orders, and such interactions may play a key role in iron-based superconductivity.

arXiv commentsupplemental material available upon request, to be published in PRL

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Cited by in corpus (4)

• Orbital selectivity in electron correlations and superconducting pairing of iron-based superconductors
• Strain-induced spin-nematic state and nematic susceptibility arising from $2\times 2$ Fe clusters in KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$
• Anisotropic magnetic excitations of a frustrated bilinear-biquadratic spin model -- Implications for spin waves of detwinned iron pnictides
• Twinning of domains and spin anisotropy in K${}_5$Fe${}_4$Ag${}_6$Te${}_{10}$