Doping-dependent energy scale of the low-energy band renormalization in (Bi,Pb)2(Sr,La)2CuO6+d

TL;DR

This study reveals a doping-dependent low-energy band renormalization in (Bi,Pb)2(Sr,La)2CuO6+d, showing a scaling with Tc and a sharp increase in coupling energy near optimal doping, highlighting strong electron correlation effects.

Contribution

It demonstrates the existence and doping dependence of a low-energy kink in Bi2201, linking mode-coupling energy to Tc and electron correlation, expanding understanding of high-Tc cuprates.

Findings

Low-energy kink occurs in Bi2201 at half the energy of Bi2212.

Coupling energy increases sharply with decreasing doping, especially near optimal doping.

Doping dependence of the low-energy mode-coupling correlates with Tc and electron correlation.

Abstract

The nodal band-dispersion in (Bi,Pb)2(Sr,La)2CuO6+d (Bi2201) is investigated over a wide range of doping by using 7-eV laser-based angle-resolved photoemission spectroscopy. We find that the low-energy band renormalization ("kink"), recently discovered in Bi2Sr2CaCu2O8+d (Bi2212), also occurs in Bi2201, but at a binding energy around half that in Bi2212, implying its scaling to Tc. Surprisingly the coupling-energy dramatically increases with a decrease of carrier concentration, showing a sharp enhancement across the optimal doping. This strongly contrasts to other mode-couplings at higher binding-energies (~20, ~40, and ~70 meV) with almost no doping variation in energy scale. These nontrivial properties of the low-energy kink (material- and doping-dependence of the coupling-energy) demonstrate the significant correlation among the mode-coupling, the Tc, and the strong electron correlation.