Ground state instability in spin polarization for electrons confined in two-dimensional square quantum dots

Yhuki Negishi, Masamu Ishizuki, Takuma Okunishi, Kyozaburo Takeda

    Research output: Contribution to journalArticle

    2 Citations (Scopus)

    Abstract

    We present a theoretical study of the ground state electronic structure and the spin polarization for four electrons confined in two-dimensional (2D) square quantum dots (SQDs). We employ standard mean field theory (MFT) approaches using the unrestricted Hartree-Fock (UHF) and density functional theory calculations. The resonant UHF configuration interaction (res-UHF CI) calculation was also performed in order to incorporate the electron correlation more intuitively. The MFT ground state is expected to be spin-polarized when SQDs have a small confinement length L or aspect ratio δ = L x/Ly = 1, in agreement with Hund's rule. In contrast, the spin-unpolarized ground state singlet is expected in all in other SQDs. Thus, the MFT calculations produce the anti-Hund state, where the spin-density wave forms having the zero of the total spin, even though the SQD has the point group symmetry D4h. However, the res-UHF CI calculation restores the geometrical symmetry in the resulting ground state when the Coulomb interaction is strengthened. Nevertheless, the res-UHF CI ground state maintains the zero total spin. Thus, ground state instability is expected in the spin-polarization of the SQD system, which eventually violates Hund's rule in accordance with the Coulomb interaction.

    Original languageEnglish
    Article number085001
    JournalJapanese Journal of Applied Physics
    Volume50
    Issue number8 PART 1
    DOIs
    Publication statusPublished - 2011 Aug

    Fingerprint

    Spin polarization
    Ground state
    Semiconductor quantum dots
    quantum dots
    Mean field theory
    ground state
    Electrons
    polarization
    electrons
    configuration interaction
    Crystal symmetry
    Coulomb interactions
    Spin density waves
    Point groups
    Electron correlations
    symmetry
    Electronic structure
    Density functional theory
    Aspect ratio
    aspect ratio

    ASJC Scopus subject areas

    • Engineering(all)
    • Physics and Astronomy(all)

    Cite this

    Ground state instability in spin polarization for electrons confined in two-dimensional square quantum dots. / Negishi, Yhuki; Ishizuki, Masamu; Okunishi, Takuma; Takeda, Kyozaburo.

    In: Japanese Journal of Applied Physics, Vol. 50, No. 8 PART 1, 085001, 08.2011.

    Research output: Contribution to journalArticle

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