Coupling to a phononic mode in $Bi_{2-x}Pb_xSr_2CaCu_2O_{8+\delta}$: Angle-resolved photoemission

TL;DR

This study uses angle-resolved photoemission to analyze the coupling of electrons to a phononic mode in Bi-based cuprates, revealing new criteria for identifying the interaction energy scale and clarifying the origin of spectral features.

Contribution

It demonstrates that the kink and width drop in the dispersion are caused by electron-phonon coupling, providing a new method to determine the interaction energy scale.

Findings

The kink and width drop are due to electron-phonon coupling.

Peak height can be used as a new criterion for interaction energy.

Optimally lead-doped Bi2212 shows these features, extending previous studies.

Abstract

The kink in the dispersion and the drop in the width observed by angle-resolved photoemission in the nodal direction of the Brillouin zone of $\mathrm{Bi_{2-x}Pb_xSr_2CaCu_2O_{8+ \delta}}$ (abbreviated as (Pb)Bi2212) has attracted broad interest [1-3]. Surprisingly optimally lead-doped (Pb)Bi2212 with $\mathrm{T_C>89K}$ as well as the shadow band were not investigated so far, although the origin of the kink and the drop is still under strong debate. In this context a resonant magnetic-mode scenario and an electron-phonon coupling scenario are discussed controversially. Here we analyze the relevant differences between both scenarios and conclude that the kink and the drop are caused by a coupling of the electronic system to a phononic mode at least in the nodal direction. It is found that besides the dispersion and the drop in the width also the peak height as a new criterion can be used to define the energy scale of the interaction, giving a new means for a precise and consistent determination of the kink energy.