Direct evidence for predominantly phonon-mediated pairing in high-temperature superconductors

TL;DR

This study provides direct experimental evidence that phonons are the primary mediators of electron pairing in high-temperature superconductors, linking tunneling spectra features with phonon density of states.

Contribution

It establishes a clear connection between tunneling spectroscopy features and phonon modes, demonstrating phonons' dominant role in high-temperature superconductivity.

Findings

Peaks in tunneling spectra match phonon density of states.

Bosonic modes mediating pairing are phonons.

Superconductivity arises mainly from strong phonon coupling.

Abstract

The spectra of the second derivative of tunneling current d^{2}I/dV^{2} in the high-temperature superconductors YBa_{2}Cu_{3}O_{7-\delta} and Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} show clear dip and peak features due to strong coupling to the bosonic modes mediating electron pairing. The energies of all the peaks in -d^{2}I/dV^{2}-like spectra match precisely with the energies of the peaks in the phonon density of states obtained by inelastic neutron scattering. The results clearly demonstrate that the bosonic modes mediating the electron pairing are phonons and that high-temperature superconductivity arises primarily from strong coupling to multiple phonon modes.