Enhanced Electron-Phonon Coupling and its Irrelevance to High T$_{c}$ Superconductivity

TL;DR

This paper investigates the origin of buckling in cuprate planes and the role of electron-phonon coupling, concluding that despite strong coupling, it is not the primary driver of high-temperature superconductivity.

Contribution

The study links electric fields caused by atomic valence differences to electron-phonon coupling, showing it is not directly responsible for high T$_{c}$ superconductivity.

Findings

Electric fields induce buckling and strong electron-phonon coupling.

Yttrium doping enhances coupling but reduces T$_{c}$.

Electron-phonon coupling is irrelevant to high T$_{c}$ superconductivity.

Abstract

It is argued that the origin of the buckling of the CuO$_{2}$ planes in certain cuprates as well as the strong electron-phonon coupling of the $B_{1g}$ phonon is due to the electric field across the planes induced by atoms with different valence above and below. The magnitude of the electric field is deduced from new Raman results on YBa$_{2}$Cu$_{3}$O$_{6+x}$ and Bi$_{2}$Sr$_{2}$(Ca$_{1-x}$Y$_{x}$)Cu$_{2}$O$_{8}$ with different O and Y doping, respectively. In the latter case it is shown that the symmetry breaking by replacing Ca partially by Y enhances the coupling by an order of magnitude, while the superconducting $T_c$ drops to about two third of its original value.