Electronic phase diagram in Te-annealed superconducting FeTe${}_{1-x}$Se${}_x$ revealed by magnetic susceptibility

Abstract

Knowledge of the doping (x)-temperature (T) phase diagram of Fe-based superconductors is crucial in understanding the mechanism of high transition temperature superconductivity. Here, we measured the Se doping dependence of the magnetic susceptibility for Te-annealed FeTe${}_{1-x}$Se${}_x$. Two characteristic temperatures $T_{\chi }^{\ast }$ and $T_{\chi }^{\ast \ast }$ were observed in the temperature dependence of magnetic susceptibility, where the magnetic susceptibility decreased below T${}_{\chi }^{\ast \ast }$ and tended to increase with further decreasing temperature below T${}_{\chi }^{\ast }$. The decrease in magnetic susceptibility below T${}_{\chi }^{\ast \ast }$ is considered to be due to the opening of the pseudogap. Whereas the increase in magnetic susceptibility below T${}_{\chi }^{\ast }$ is attributed to the increase in the carrier concentration of electrons. Furthermore, we found the large superconducting fluctuation, which may be related to BCS-BEC crossover.

6 pages, 3 figures. to be published in JPS Conference Proceedings

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