Upper limit for superconducting transition temperature in Eliashberg-McMillan theory

TL;DR

This paper provides qualitative estimates for the maximum superconducting transition temperature achievable through electron-phonon coupling within Eliashberg-McMillan theory, linking it to atomic constants and electron density.

Contribution

It introduces a simple estimate for the upper limit of superconducting transition temperature based on strong coupling limits in Eliashberg-McMillan theory.

Findings

Upper limit determined by atomic constants and electron density.

In the strong coupling limit, transition temperature is bounded.

Provides a theoretical maximum for superconducting T_c.

Abstract

We present simple qualitative estimates for the maximal superconducting transition temperature, which may be achieved due to electron - phonon coupling in Eliashberg-McMillan theory. It is shown that in the limit of very strong coupling the upper limit for transition temperature is determined in fact by a combination of atomic constants and density of conduction electrons.