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 λVH was found to increase with transition temperature TcTc. λVH 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 θDθD does not correlate with TcTc. 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.