Unrestricted Hartree-Fock for Quantum Dots

Abstract

We present detailed results of Unrestricted Hartree-Fock (UHF) calculations for up to eight electrons in a parabolic quantum dot. The UHF energies are shown to provide rather accurate estimates of the ground-state energy in the entire range of parameters from high densities with shell model characteristics to low densities with Wigner molecule features. To elucidate the significance of breaking the rotational symmetry, we compare Restricted Hartree-Fock (RHF) and UHF. While UHF symmetry breaking admits lower ground-state energies, misconceptions in the interpretation of UHF densities are pointed out. An analysis of the orbital energies shows that for very strong interaction the UHF Hamiltonian is equivalent to a tight-binding Hamiltonian. This explains why the UHF energies become nearly spin independent in this regime while the RHF energies do not. The UHF densities display an even-odd effect which is related to the angular momentum of the Wigner molecule. In a weak transversal magnetic field this even-odd effect disappears.

arXiv comment13 pages, 14 figures, submitted 30. Oct. 2002, to appear in PRB. For a version with high-quality figures, see http://www.thphy.uni-duesseldorf.de/~reusch/index.html

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• Validity of the single-particle description and charge noise resilience for multielectron quantum dots
• Accuracy of the Hartree-Fock method for Wigner molecules at high magnetic fields
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• Brueckner-Hartree-Fock study of circular quantum dots
• The violation of the Hund's rule in semiconductor artificial atoms
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• Exact broken-symmetry states and Hartree-Fock solutions for quantum dots at high magnetic fields
• Path-integral Monte Carlo study of electronic states in quantum dots in an external magnetic field
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