Importance of structural distortions in enhancement of transition temperature in FeSe${}_{1-x}$Te${}_x$ superconductors

Abstract

Temperature (12K $\le$ T $\le$ 300K) dependent extended X-ray absorption fine structure (EXAFS) studies at the Fe K edge in FeSe${}_{1-x}$Te${}_x$ (x = 0, 0.5 and 1.0) compounds have been carried out to understand the reasons for increase in T${}_C$ upon Te doping in FeSe. While local distortions are present near superconducting onset in FeSe and FeSe${}_{0.5}$Te${}_{0.5}$, they seem to be absent in non superconducting FeTe. Of crucial importance is the variation of anion height. In FeSe${}_{0.5}$Te${}_{0.5}$, near superconducting onset, the two heights, $h_{Fe-Se}$ and $h_{Fe-Te}$ show a nearly opposite behaviour. These changes indicate a possible correlation between Fe-chalcogen hybridization and the superconducting transition temperature in these Fe-chalcogenides.

Accepted for publication in Superconductor Science and Technology

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