Suppression of Superconductivity and Nematic Order in Fe${}_{1-y}$Se${}_{1-x}$S${}_x$ (0$\le$$x$$\le$1, $y$$\le$0.1) Crystals by Anion Height Disorder

Abstract

Connections between crystal chemistry and critical temperature $T_c$ have been in the focus of superconductivity, one of the most widely studied phenomena in physics, chemistry and materials science alike. In most Fe-based superconductors, materials chemistry and physics conspire so that $T_c$ correlates with the average anion height above the Fe plane, i. e. with the geometry of the FeAs4 or FeCh4 (Ch = Te, Se, or S) tetrahedron. By synthesizing Fe${}_{1-y}$Se${}_{1-x}$S${}_x$ (0$\le$$x$$\le$1, $y$$\le$0.1), we find that in alloyed crystals $T_c$ is not correlated with the anion height like it is for most other Fe superconductors. Instead, changes in $T_c$($x$) and tetragonal-to-orthorombic (nematic) transition $T_s$($x$) upon cooling are correlated with disorder in Fe vibrations in the direction orthogonal to Fe planes, along the crystallographic c-axis. The disorder stems from the random nature of S substitution, causing deformed Fe(Se,S)4 tetrahedra with different Fe-Se and Fe-S bond distances. Our results provide evidence of $T_c$ and $T_s$ suppression by disorder in anion height. The connection to local crystal chemistry may be exploited in computational prediction of new superconducting materials with Fe/S building blocks.

10 pages, 5 figures

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Cited by in corpus (1)

• Evolution of lattice, spin, and charge properties across the phase diagram of FeSe${}_{1-x}$S${}_x$