Enhanced superconducting transition temperatures in the rocksalt-type superconductors In1−xSnxTe (x≤0.5)

Abstract

We investigate superconductivity in ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Sn}}_{x}\mathrm{Te}$ ($x\ensuremath{\le}0.5$) synthesized at high pressures of up to 2 GPa and observe an enhancement of the superconducting transition temperature ${T}_{\mathrm{c}}$ for increasing tin concentration $x$. These compounds have not been accessible in rocksalt structure via conventional ambient pressure synthesis. While the lattice constant smoothly increases with $x$, ${T}_{\mathrm{c}}$ saturates around $x=0.4$. Electronic structure calculations indicate that the ${T}_{\mathrm{c}}$ modulation is brought on by the change of the density of states in the vicinity of the Fermi energy $[N({E}_{\mathrm{F}})]$. However, differences between the calculated $N({E}_{\mathrm{F}})$ and the observed electronic specific-heat coefficient indicate that the phonon dispersion plays an important role in the system and that the mechanism of superconductivity may not be the same in the entire doping range.