Energy-Dependent Enhancement of the Electron-Coupling Spectrum of the Underdoped Bi2Sr2CaCu2O8+d Superconductor

TL;DR

This study reveals how the electron-coupling spectrum in underdoped Bi2Sr2CaCu2O8+d superconductors varies with doping, showing energy-dependent enhancements and suppressions that suggest complex screening effects.

Contribution

We introduced two robust, deconvolution-free methods to determine the electron-coupling spectrum from high-resolution ARPES data, revealing doping-dependent spectral weight changes.

Findings

Low-energy coupling (~<15 meV) doubles with decreased hole doping.

Moderate increase in coupling around ~65 meV with doping change.

Decrease in coupling at energies >130 meV, indicating a crossover of dominant excitations.

Abstract

We have determined the electron-coupling spectrum of superconducting Bi2Sr2CaCu2O8+d from high-resolution angle-resolved photoemission spectra by two deconvolution-free robust methods. As hole concentration decreases, the coupling spectral weight at low energies ~<15 meV shows a twofold and nearly band-independent enhancement, while that around ~65 meV increases moderately, and that in ~>130 meV decreases leading to a crossover of dominant coupling excitation between them. Our results suggest the competition among multiple screening effects, and provide important clues to the source of sufficiently strong low-energy coupling, {\lambda}LE ~ 1, in underdoped system.