Excitation energy map of the high-energy dispersion anomalies in cuprates

TL;DR

This study maps the high-energy dispersion anomalies in cuprate superconductors using ARPES, revealing photon energy-dependent behaviors driven mainly by photoemission matrix elements rather than band interactions or three-dimensional effects.

Contribution

It provides a detailed excitation energy map of high-energy dispersion anomalies in cuprates, clarifying their origin as mainly due to photoemission matrix elements.

Findings

Two types of dispersion behavior alternate with photon energy.

Transitions between behaviors occur near specific photon energies.

Photon energy dependence is not due to band interactions or 3D effects.

Abstract

The anomalous high-energy dispersion of the conductance band in the high-Tc superconductor Pb-Bi2212 has been extensively mapped by angle-resolved photoemission (ARPES) as a function of excitation energy in the range from 34 to 116 eV. Two distinctive types of dispersion behavior are observed around 0.6 eV binding energy, which alternate as a function of photon energy. The continuous transitions observed between the two kinds of behavior near 50, 70, and 90 eV photon energies allow to exclude the possibility that they originate from the interplay between the bonding and antibonding bands. The effects of three-dimensionality can also be excluded as a possible origin of the excitation energy dependence, as the large period of the alterations is inconsistent with the lattice constant in this material. We therefore confirm that the strong photon energy dependence of the high-energy dispersion in cuprates originates mainly from the photoemission matrix element that suppresses the photocurrent in the center of the Brillouin zone.