Ground State Instability in Spin Polarization for Electrons Confined in Two-Dimensional Square Quantum Dots
| Autor: | Kyozaburo Takeda, Yhuki Negishi, Masamu Ishizuki, Takuma Okunishi |
|---|---|
| Rok vydání: | 2011 |
| Předmět: |
Physics
Physics and Astronomy (miscellaneous) Spin polarization Condensed matter physics Electronic correlation General Engineering General Physics and Astronomy Electronic structure Configuration interaction Quantum mechanics Condensed Matter::Strongly Correlated Electrons Density functional theory Singlet state Ground state Spin-½ |
| Zdroj: | Japanese Journal of Applied Physics. 50:085001 |
| ISSN: | 1347-4065 0021-4922 |
| DOI: | 10.1143/jjap.50.085001 |
| Popis: | 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 /L y = 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 D 4h . 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. |
| Databáze: | OpenAIRE |
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