Predictions of highest transition-temperature for electron–phonon superconductors

Using the Eliashberg strong-coupling theory with vertex correction, we calculate maps of transition temperatures (Tc)(Tc) of electron–phonon superconductors in full parameter space. The maximums of transition temperatures for superconductors are predicted based on the maps and the criterion of instability of superconductivity. The strong vertex correction and high transition-temperature are tightly correlated in superconductors. We predict that the maximum of TcTc of new iron-based superconductors will be close to 90 (K).