Fig. 3
Evolution of the superconducting dome with La substitution and 18O exchange. a Tc vs. n plot for the Sr1−xLaxTi(16O1−z18Oz)3 single crystals shown in Figs. 1a and 2a. The upper and lower error bars are determined from the onset and end temperatures of the superconductivity (see Supplementary Figure 4). Tc for SrTiO3−δ21,28,31, SrTi1−xNbxO331,34, and La-substituted SrTiO327 are also plotted. b The lines were obtained from calculations based on the model in ref. 18, which are compared with some of the experimental data in a. c Tunnelling energy Γ vs. Fermi temperature TF deduced from the experimental values of Tc and n using Supplementary Equations 1 and 2: Sr1−xLaxTiO3 (red squares) and Sr1−xLaxTi(16O1−z18Oz)3 (z = 0.6; x ~ 0.002, 0.0035, and 0.01) (blue squares) from this study; SrTiO3−δ (black circles) from the literature21. The experimental data were fitted by the lines of Γ = A + BTF + CTF2. From these fitting results for Γ, we obtained the Tc vs. n relation represented by the lines in b. d The blow-up of c to emphasise where the Γ crosses Γ = 1 line
