"Waterfalls" in cuprates

TL;DR

This paper investigates the 'waterfalls' observed in ARPES spectra of cuprates, revealing they are artifacts caused by matrix-element effects rather than intrinsic features, and clarifies the true electronic structure.

Contribution

It demonstrates that the waterfalls are artificial features resulting from matrix-element effects, providing a clearer understanding of the ARPES spectra in cuprates.

Findings

Waterfalls are artifacts caused by matrix-element suppression.

The true electronic structure shows a grid-like pattern in the BZ.

The 0.2-0.3 eV energy scale is linked to bosonic coupling, not waterfalls.

Abstract

New hot topic in ARPES on HTSC, the observation of the so called "waterfalls", is addressed. The energy scale at about 0.2-0.3 eV that can be derived from the coherent component of ARPES spectra measured along the nodal direction is not new but has been already discussed in terms of a coupling to a bosonic continuum. However, the waterfalls, namely the long vertical parts of the experimental dispersion around the center of the Brillouin zone (BZ), seem to be purely artificial. They are a consequence of simple matrix-element effect: a complete suppression of the photoemission intensity from both the coherent and "incoherent" components. When the matrix-elements are taken into account, the latter reveals a grid-like structure along the bonding directions in the BZ.