On the cuprates' universal waterfall feature: evidence of a momentum-driven crossover

TL;DR

This paper investigates the universal waterfall and high-energy kink features in cuprates' spectral functions, attributing them to a momentum-driven crossover influenced by spin-polaron and local correlation effects, with implications for superconductivity.

Contribution

It introduces a unified explanation for the waterfall and kink features in cuprates, linking them to a momentum-dependent crossover driven by spin-polaron interactions.

Findings

Waterfall and kink features are universal in cuprates.

These features originate from a momentum-driven crossover.

The scenario applies across doping levels within the superconducting dome.

Abstract

We study two related universal anomalies of the spectral function of cuprates, so called waterfall and high-energy kink features, by a combined cellular dynamical mean-field theory and angle-resolved photoemission study for the oxychloride Na$_x$Ca$_{2-x}$CuO$_2$Cl$_2$ (Na-CCOC). Tracing their origin back to an interplay of spin-polaron and local correlation effects both in undoped and hole-doped (Na-)CCOC, we establish them as a universal crossover between regions differing in the momentum dependence of the coupling and not necessarily in the related quasiparticles' energies. The proposed scenario extends to doping levels coinciding with the cuprate's superconducting dome and motivates further investigations of the fate of spin-polarons in the superconducting phase.