Superconductivity and the fct-fcc transformation in indium-thallium alloys as a function of pressure.

Abstract

The pressure dependence of the superconducting transition temperature (${\mathit{T}}_{\mathit{c}}$) has been determined up to \ensuremath{\sim}2.5 GPa for solid-solution In-Tl alloys with compositions between 31.5 and 36.5 at. % Tl. The cusp in ${\mathit{T}}_{\mathit{c}}$ as a function of composition, that has been associated with the fcc-fct phase boundary at zero pressure, is found to move to higher thallium concentrations with increasing pressure. This is interpreted as a pressure-induced stabilization of the fct phase resulting from changes in the Fermi surface--Brillouin zone boundary overlap.