On the nature of dispersion of the polaronic bands in ARPES spectra of cuprates: supplement of the Franck-Condon principle

TL;DR

This paper investigates the dispersion of polaronic bands in ARPES spectra of cuprates, attributing it to recoil momentum within the Frohlich-Pekar polaron model, and enhances the analytical description to match experimental observations.

Contribution

It introduces an improved analytical model accounting for recoil momentum, explaining polaronic band dispersion without relying solely on spin correlations.

Findings

Dispersion arises from recoil momentum, not spin correlations.

The model's predictions align well with experimental ARPES data.

Polaron effective mass can be extracted from the dispersion analysis.

Abstract

Spin correlations are considered now as the only possible source of dispersion of the polaronic band in ARPES spectra of cuprates. However, the same dispersion is observed experimentally for broad O 2p{\pi} band in ARPES spectra of cuprates [Phys. Rev. B 75, 075115 (2007)] although the O 2p{\pi} states do not experience any coupling to the low-energy spin degrees of freedom. The aim of the present report is exploring dispersion of the polaronic band in ARPES spectrum in the frames of Frohlich-Pekar polaron model where this band is calculated analytically [Phys. Rev. B 77, 165136 (2008)]. We improve the method by taking into account the momentum of the recoil and obtain new analytical expression for the photoelectron rate as function of binding energy and momentum. Calculated according to it polaronic band demonstrates dispersion and broadening being in good agreement with the experiment. The dispersion is caused by the momentum of the recoil and can be used to extract the polaron effective mass from the experimental ARPES spectra. We also supplement the Franck-Condon principle by indication that if the phonon field is in a coherent state then during rapid (photo) transition the average coordinates of the phonon field harmonics do not change, but their average momentums are changed due to the recoil momentum.