Spontaneous symmetry breaking in single and molecular quantum dots

TL;DR

This paper explores spontaneous symmetry breaking phenomena in single and molecular quantum dots at low magnetic fields, revealing different electron localization and spin structures depending on the Coulomb interaction strength.

Contribution

It provides a detailed analysis of symmetry breaking in quantum dots using advanced Hartree-Fock calculations, including new findings on spin polarizations after further systematic studies.

Findings

Wigner crystallization occurs for R_W > 1

Electron puddles form in quantum dot molecules for R_W < 1

Violation of Hund's first rule observed in certain cases

Abstract

Classes of spontaneous symmetry breaking at zero and low magnetic fields in single quantum dots (QD's) and quantum dot molecules (QDM's) are discussed in relation to the ratio R_W between the interelectron Coulomb repulsion and the harmonic confinement, using spin-and-Space unrestricted Hartree-Fock calculations. These include: Wigner crystallization for R_W > 1, and formation of non-crystallized electron puddles localized on the individual dots in QDM's, as well as spin-density waves in single QD's, for R_W < 1. Erratum: Subsequent to the the publication of our Letter, we have performed further systematic spin-and-space unrestricted Hartree-Fock calculations. While the behavior and magnitudes of the addition energies shown in our Letter are maintained, as well as our finding pertaining to the prevalent violation of Hund's first rule, our improved calculations yield in certain instances different spin polarizations.