Superconductivity in Ge_1-xIn_xTe

Variation of physical quantities in ${\mathrm{Ge}}_{1-x}{\mathrm{In}}_x\mathrm{Te}$. (a) Pseudocubic unit-cell volume for rhombohedral ( $x<0.12$) and cubic structure ( $x>0.12$) at 300 K. (b) Zero-field resistivity at 300 K (red open symbols) and at low $T$ (blue filled symbols; at 2 K for $x\le 0.25$ and above $T_c$ for larger $x$). (c) Charge-carrier concentration $n$ at 300 K. Note that $n$ for $x\ge 0.25$ (dashed-dotted vertical line) are multiplied by 0.1 for clarity. (d) Superconducting $T_c$ as estimated from resistivity, specific heat, and magnetization. The error bars for data points below $x=0.16$ indicate that these samples do not superconduct down to approx. 400 mK. (e) Normal-state electronic specific-heat coefficients ${\gamma }_n$. (f) Electron-phonon coupling strength deduced from specific-heat data. Dotted lines are guides to the eyes, solid horizontal lines in (c)–(e) indicate baselines, and the dashed vertical lines denote $x_c=0.12$.