High-Temperature Superconductivity—An Electron Transfer Phenomenon

The increase of the critical temperature T_c for superconductivity in Al_1？x(SiO₂)_x cermets with increasing x correlates with a decrease of the electron density n due to electron transfer, expressed by $T_c/T_{c,\max }=1？\gamma ？n^2$ (*). Behind the formula (*) and $T_c/T_{c,\max }=1？82.6{\left(P？0.16\right)}^2$ , which is characteristic of hole-doped cuprat high-temperature superconductors, lies a general phenomenon, namely electron transfer, which equalizes potential differences in the material and leads to a strong reduction of n. P is the fraction of holes filled by the transferred electrons. A quantitative consideration gives $T_c\left(x\right)/T_{c,\max }=1？{\left(\frac{1？x}{1？x_0}\right)}^2$ (**), where x is the doping concentration and x₀ is the concentration at which superconductivity begins. At $x={}_{}$