Intriguing electron correlation effects in the photoionization of metallic quantum--dot nanorings

TL;DR

This paper investigates ionization in metallic quantum-dot nanorings using the extended Hubbard model, revealing a hidden quasi-symmetry that explains the scarcity of ionization signals despite strong electron correlations.

Contribution

It uncovers a hidden quasi-symmetry in the extended Hubbard model affecting ionization spectra and links ionization signals to noninteracting processes, offering new insights into electron correlations.

Findings

Ionization spectra are surprisingly scarce despite strong correlations.

A hidden quasi-symmetry influences ionization signals.

Ionization provides complementary information to optical absorption.

Abstract

We report detailed results on ionization in metallic quantum--dot (QD) nanorings described by the extended Hubbard model at half filling obtained by exact numerical diagonalization. In spite of very strong electron correlations, the ionization spectra are astonishingly scarce. We attribute this scarcity to a hidden quasi--symmetry, generalizing thereby similar results on optical absorption recently reported [I. Baldea and L. S. Cederbaum, \prb {\bf 75}, 125323 (2007); {\bf 77}, 165339 (2008)]. Numerical results indicate that this hidden quasi--symmetry of the extended Hubbard model does not evolve into a true (hidden) symmetry but remains a quasi--symmetry in the case of the restricted Hubbard model as well. Based on the observation on the number of significant ionization signals per each spatial symmetry, we claim the existence of a one--to--one map between the relevant ionization signals of the correlated half-filled nanorings and the one-hole and two-hole--one-particle processes possible in the noninteracting case. Similar to the case of optical absorption, numerous avoided crossings (anticrossings) are present in the ionization spectra, which often involve more than two states. The present results demonstrate that ionization could be a useful tool to study electron correlations in metallic QD--nanoarrays, providing information that is complementary to optical absorption.