Abstract
The Eliashberg expression for the free-energy difference between superconducting and normal states for an electron-phonon interaction model is evaluated so as to estimate the errors involved in expressions based on the weak-coupling limit. It is shown that the major correction comes from the difference in self-energy terms and and is relatively of order , where is an average phonon energy. The correction may be appreciable for strong-coupling superconductors such as lead.
- Received 27 July 1964
DOI:https://doi.org/10.1103/PhysRev.136.A1485
©1964 American Physical Society