Figure 1

(Color online) Effect of indium substitution in ${\text{Pb}}_{0.99-y}{\text{Tl}}_{0.01}{\text{In}}_y\text{Te}$ as a function of indium content $y$ on (a) the Hall number, $n_H$; (b) the residual resistance ratio, $\text{RRR}=\rho \left(300\text{K}\right)/\rho \left(1.8\text{K}\right)$; (c) an estimate of the magnitude of the low-temperature resistance upturn, $\Delta \rho =\rho \left(1.8\text{K}\right)-\rho \left(\text{min}\right)$; (d) the electronic coefficient to the specific heat, $\gamma$ (left axis), and the corresponding density of states per spin at the Fermi level, $N\left(0\right)$ (right axis); and (e) the superconducting critical temperature, $T_c$, derived from heat-capacity measurements. Lines are drawn between data points as a guide to the eye. The data delineate two distinct regimes. For concentrations $y\le 0.8\mathrm{\%}$ (solid blue shading) samples have a large hole density, superconduct, and exhibit anomalous low-temperature scattering. For concentrations $y\ge 1.4\mathrm{\%}$ (no shading) the Fermi level moves steadily up in to the conduction band, the material does not superconduct above 50 mK, and there is no resistivity upturn at low temperature (no shading). Crossover behavior between these two regimes (graded shading for $0.8<y<1.4\mathrm{\%}$) is characterized by intermediate values of the RRR and $\gamma$.Reuse & Permissions

Figure 2

(Color online) Representative resistivity data for ${\text{Pb}}_{0.99-y}{\text{Tl}}_{0.01}{\text{In}}_y\text{Te}$ between 1.8 and 300 K, normalized to the value at 300 K for clarity. Data are labeled by the In content. For In concentrations above 0.8% there is a substantial reduction in the residual resistivity and corresponding increase in the RRR.Reuse & Permissions

Figure 3

(Color online) Temperature dependence of the resistivity of ${\text{Pb}}_{0.99-y}{\text{Tl}}_{0.01}{\text{In}}_y\text{Te}$ at low temperatures for four representative In concentrations. For $y\le 1.2\mathrm{\%}$ a low-temperature upturn is observed.Reuse & Permissions

Figure 4

(Color online) (a) Representative data showing the temperature dependence of the heat capacity of ${\text{Pb}}_{0.99-y}{\text{Tl}}_{0.01}{\text{In}}_y\text{Te}$ with $0<y<2.1\mathrm{\%}$, shown as $C_p/T$. Inset shows the normalized heat-capacity jump, $\Delta C_p/\gamma T_c$, as a function of the indium concentration, $y$, as described in the main text. The horizontal line in the inset represents the BCS weak coupling prediction of $\Delta C/\gamma T_c=1.43$. (b) ${\text{C}}_p/T$ as a function of $T^2$, for the same samples shown in panel (a). Lines are linear fits to data taken below 1 K, from which the Sommerfeld coefficient, $\gamma$, is extracted.Reuse & Permissions