Doping dependence of the coupling of electrons to bosonic modes in the single-layer high-temperature Bi2Sr2CuO6 superconductor

TL;DR

This study investigates how electron coupling to bosonic modes in Bi2Sr2CuO6 varies with doping, revealing a weakening and energy shift of self-energy effects linked to changes in phonon coupling and c-axis screening.

Contribution

First comparison of self-energies in optimally doped and overdoped Bi2Sr2CuO6, showing doping-dependent changes in electron-boson coupling and phonon interactions.

Findings

Self-energy effects weaken with overdoping.

Shift of self-energy weight to higher energies in overdoped samples.

Change in c-axis phonon coupling linked to doping level.

Abstract

A recent highlight in the study of high-Tc superconductors is the observation of band renormalization / self-energy effects on the quasiparticles. This is seen in the form of kinks in the quasiparticle dispersions as measured by photoemission and interpreted as signatures of collective bosonic modes coupling to the electrons. Here we compare for the first time the self-energies in an optimally doped and strongly overdoped, non-superconducting single-layer Bi-cuprate (Bi2Sr2CuO6). Besides the appearance of a strong overall weakening, we also find that weight of the self-energy in the overdoped system shifts to higher energies. We present evidence that this is related to a change in the coupling to c-axis phonons due to the rapid change of the c-axis screening in this doping range.