Isomeric and hybrid isomeric-vibrational states of Wigner molecules

Abstract

An accurate configuration-interaction method employing a numerical mean-field basis set is used to study the excitation spectrum of Wigner molecules, including isomeric excitations, in small parabolic quantum dots. We find that at intermediate electron densities $({r}_{s}\ensuremath{\sim}8{a}_{0}^{\ensuremath{\ast}}--20{a}_{0}^{\ensuremath{\ast}})$, in the regime of strong interaction and partial Wigner localization, there are inversions of the usual Born-Oppenheimer ordering of isomeric and vibrational excitations, yielding low-lying isomeric excitations. Quantum-mechanical hybridization of different isomers can occur near an avoided crossing of a vibrational and an isomeric excitation. These findings suggest the possibility of observing isomers and hybrid isomeric-vibrational states experimentally.