Doping dependence of the mass enhancement in (Pb,Bi)_2 Sr_2 Ca Cu_2 O_8 at the antinodal point in the superconducting and normal state

TL;DR

This study uses ARPES to investigate how doping affects mass enhancement and electron-boson interactions in a high-T_c superconductor, revealing strong anisotropic coupling below T_c and weaker, more isotropic interactions above T_c.

Contribution

It provides detailed doping-dependent analysis of mass renormalization and electron-boson coupling in (Pb,Bi)_2Sr_2CaCu_2O_8 using high-resolution ARPES.

Findings

Strong anisotropic coupling below T_c, especially in underdoped samples.

Weaker, more isotropic coupling above T_c.

Separation of bonding and antibonding bands across doping levels.

Abstract

Angle-resolved photoemission spectroscopy (ARPES) is used to study the mass renormalization of the charge carriers in the high-T_c superconductor (Pb,Bi)_2Sr_2CaCu_2O_8 in the vicinity of the (pi,0) point in the superconducting and the normal state. Using matrix element effects at different photon energies and due to a high momentum and energy resolution the bonding and the antibonding bands could be separated in the whole dopant range. A huge anisotropic coupling to a bosonic collective mode is observed below T_c for both bands in particular for the underdoped case. Above T_c, the more isotropic coupling to a continuum or a mode at much higher energy is significantly weaker.