The stress dependence of superconducting parameters in pure In and Sn and in ?-phase In-Sn alloys

Abstract

We have measured the length change due to the transition from the super-conducting to the normal state in pure In and Sn and in In-Sn alloys. The measurements were made on single-crystal specimens. The alloys had Sn content ranging from zero to 12 at %. Crystals parallel and perpendicular to the tetragonal axis were grown at each alloy content. We find that the relative length changes Δl/l are very sensitive to alloy content. From Δl/l we have calculated the stress derivatives ∂Hc/∂σ and ∂T c /∂σ and we find that ∂T c /∂σ changes from +59 to −92 mK/bar for stress along the tetragonal axis, and from −9 to 46 mK/kbar for stress perpendicular to the tetragonal axis. We suggest that these large changes are due to Fermi surface topology changes upon increasing the Sn content in In.