Tellurium substitution effect on superconductivity of the α-phase iron selenide

We have carried out a systematic study of the PbO-type compound FeSe1-xTex (x = 0-1), where the Te substitution effect on superconductivity is investigated. It is found that the superconducting transition temperature reaches a maximum of T-c = 15.2 K at about 50% Te substitution. The pressure-enhanced Tc of FeSe0.5Te0.5 is more than 10 times larger than that of FeSe. Interestingly, FeTe is no longer superconducting. A low-temperature structural distortion changes FeTe from triclinic symmetry to orthorhombic symmetry. We believe that this structural change breaks the magnetic symmetry and suppresses superconductivity in FeTe. Copyright (C) EPLA, 2008