Effect of off-stoichiometry at the Fe-site in FeSe0.5Te0.5 Superconductor

Excess iron in Fe1+xSe superconductor plays a crucial role in the observation of superconductivity in this material. We have investigated the effect of off-stoichiometry at the Fe site in Fe1+xSe0.5Te0.5 (x = -0.01, 0.01 and 0.03) superconductor through magnetization, electrical transport and specific heat measurements. Our results indicate an improvement in the superconducting properties in Fe-deficient compound compared to the stoichiometric or Fe-rich compounds, in contrast to what is observed in the parent compound, FeSe.