Electron–phonon coupling constant of cuprate based high temperature superconductors

The electron–phonon coupling constant in two-dimensional cuprate high temperature superconductors has been determined by the ultrasonic method. The electron–phonon coupling constant in the Van Hove scenario λ VH was found to increase with transition temperature T c . λ VH is in the range of 0.025–0.060 which is 10–100 times smaller than the conventional three-dimensional Bardeen–Cooper–Schrieffer coupling constant. The characteristic Debye temperature θ D does not correlate with T c . These findings show that the interplay between the Debye frequency and electron–phonon coupling in the two-dimensional system and their variations have a combined effect in governing the transition temperature.