Tuning the Electron–Phonon and Superconducting Coupling in InPb Bimetallic Alloys

Electron–phonon coupling is a fundamental inelastic interaction in solid-state physics and superconductors. Here we probe electron–phonon and superconducting coupling strength by tuning the indium composition in In q Pb1–q superconducting bimetallic alloys. A crossover from weak to strong coupling strength was observed through the analysis of crystal structure and superconducting phase diagrams. The hole-doped Pb solid solution showed suppressed T C and subverted coupling strength due to decreased density of state N(0) and hardened phonons, while the electron-doped In solid solution revealed enhanced T C and stronger coupling strength because of increased N(0) and softened phonons. Our results are in agreement with the Ginzburg–Landau theory calculations regarding the dirty limits and are well described by the Allen and Dynes formula within the framework of the McMillan formalism.