Insights on the cuprate high energy anomaly observed in ARPES

TL;DR

This paper investigates the high energy anomaly in cuprate superconductors observed via ARPES, attributing it to strong electronic correlations modeled by the Hubbard Hamiltonian, which explains the anomaly's presence across different doping levels.

Contribution

The study provides a unifying theoretical framework using the Hubbard model to explain the high energy anomaly across various cuprate phases, emphasizing correlation effects over photoemission matrix elements.

Findings

The high energy anomaly marks a transition from quasiparticle to valence bands.

Correlations in the Hubbard model are key to understanding the anomaly.

The model captures doping-dependent spectral weight transfer.

Abstract

Recently, angle-resolved photoemission spectroscopy has been used to highlight an anomalously large band renormalization at high binding energies in cuprate superconductors: the high energy "waterfall" or high energy anomaly (HEA). The anomaly is present for both hole- and electron-doped cuprates as well as the half-filled parent insulators with different energy scales arising on either side of the phase diagram. While photoemission matrix elements clearly play a role in changing the aesthetic appearance of the band dispersion, i.e. creating a "waterfall"-like appearance, they provide an inadequate description for the physics that underlies the strong band renormalization giving rise to the HEA. Model calculations of the single-band Hubbard Hamiltonian showcase the role played by correlations in the formation of the HEA and uncover significant differences in the HEA energy scale for hole- and electron-doped cuprates. In addition, this approach properly captures the transfer of spectral weight accompanying doping in a correlated material and provides a unifying description of the HEA across both sides of the cuprate phase diagram. We find that the anomaly demarcates a transition, or cross-over, from a quasiparticle band at low binding energies near the Fermi level to valence bands at higher binding energy, assumed to be of strong oxygen character.