Electron-boson coupling plays a key role in superconductivity for many systems. However, in copper-based high-temperature (Tc) superconductors, its relation to superconductivity remains controversial despite strong spectroscopic fingerprints. Here we use angle-resolved photoemission spectroscopy to find a striking correlation between the superconducting gap and the bosonic coupling strength near the Brillouin zone boundary in Bi2Sr2CaCu2O8+δ. The bosonic coupling strength rapidly increases from the overdoped Fermi-liquid regime to the optimally doped strange metal, concomitant with the quadrupled superconducting gap and the doubled gap-to-Tc ratio across the pseudogap boundary. This synchronized lattice and electronic response suggests that the effects of electronic interaction and the electron-phonon coupling become intimately entangled upon entering the strange metal regime, which may in turn drive a stronger superconductivity.
@article{arxiv.1809.07437,
title = {Rapid change of superconductivity and electron-phonon coupling through 19% doping in Bi2212},
author = {Yu He and Makoto Hashimoto and Dongjoon Song and Sudi Chen and Junfeng He and Inna M. Vishik and Brian Moritz and Dunghai Lee and Naoto Nagaosa and Jan Zaanen and Thomas P. Devereaux and Yoshiyuki Yoshida and Hiroshi Eisaki and Donghui Lu and Zhi-Xun Shen},
journal= {arXiv preprint arXiv:1809.07437},
year = {2018}
}