Anisotropic Pressure Effects On Superconductivity In Fe1+Yte1-Xsx

We have investigated the uniaxial and hydrostatic pressure effects on superconductivity in Fe1.07Te0.88S0.12 through magnetic susceptibility measurements down to 1.8 K. The superconducting transition temperature T-c is enhanced by out-of-plane pressure (uniaxial pressure along the c-axis); the onset temperature of the superconductivity reaches 11.8K at 0.4 GPa. In contrast, T-c is reduced by in-plane pressure (uniaxial pressure along the ab-plane) and hydrostatic pressure. Taking into account these results, it is inferred that the superconductivity of Fe1+yTe1-xSx is enhanced when the lattice constant c considerably decreases. This implies that the relationship between T-c and the anion height for Fe1+yTe1-xSx is similar to that for most iron-based superconductors. We consider the reduction of T-c by hydrostatic pressure to be due to the suppression of spin fluctuations because the system moves away from antiferromagnetic ordering, and the enhancement of T-c by out-of-plane pressure to be due to the anion height effect on T-c.