Vacancy ordering and phonon spectrum in the Fe superconductor K$_{0.8}$Fe$_{1.6}$Se$_2$

A. M. Zhang; K. Liu; J. H. Xiao; J. B. He; D. M. Wang; G. F. Chen; B. Normand; Q. M. Zhang

doi:10.1103/physrevb.85.024518

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arXiv · 1101.2168

Vacancy ordering and phonon spectrum in the Fe superconductor K$_{0.8}$Fe$_{1.6}$Se$_2$

A. M. Zhang·K. Liu·J. H. Xiao·J. B. He·D. M. Wang·G. F. Chen·B. Normand·Q. M. Zhang

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Abstract

We have performed Raman-scattering measurements on a high-quality single crystal of the recently discovered Fe-based superconductor K$_{0.8}$Fe$_{1.6}$Se$_2$ ($T_c$ = 32 K). At least thirteen phonon modes were observed in the wave number range 10$-$300 cm$^{-1}$. The spectra possess a four-fold symmetry indicative of bulk vacancy order in the Fe-deficient planes. We perform a vibration analysis based on first-principles calculations, which both confirms the ordered structure and allows a complete mode assignment. We observe an anomaly at $T_c$ in the 180 cm$^{-1}$ $A_g$ mode, which indicates a rather specific type of electron-phonon coupling.

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A. M. Zhang, K. Liu, J. H. Xiao, J. B. He, D. M. Wang, G. F. Chen, B. Normand, Q. M. Zhang. 2012-04-24. Vacancy ordering and phonon spectrum in the Fe superconductor K$_{0.8}$Fe$_{1.6}$Se$_2$. https://doi.org/10.1103/physrevb.85.024518

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