### Abstract

We theoretically study the spin multiplicity in the ground state of the square quantum dot (SQD) including four electrons, and discuss a possibility of the singlet-triplet (S/T) instability in the quantum system. As predicted by Hund's rule, the ground-state triplet appears when the DQD has a point group symmetry of D _{4h}. This ground-state triplet is also found even in the deformed SQD (D _{2h}) if the confinement length L is elongated. Consequently, the S/T instability is expected along these boundary lines. It is also worthwhile to notice that the present DFT as well as UHF calculation predicts the spin-singlet ground-state when the inter-electron interaction is strengthened (larger L) even though the SQD maintains its geometrical form of D _{4h}. The strong electron-localization causes the destabilization in the orbital (kinetic) energies, and produces this characteristic "anti-Hund" state.

Original language | English |
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Title of host publication | AIP Conference Proceedings |

Pages | 497-498 |

Number of pages | 2 |

Volume | 1399 |

DOIs | |

Publication status | Published - 2011 |

Event | 30th International Conference on the Physics of Semiconductors, ICPS-30 - Seoul Duration: 2010 Jul 25 → 2010 Jul 30 |

### Other

Other | 30th International Conference on the Physics of Semiconductors, ICPS-30 |
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City | Seoul |

Period | 10/7/25 → 10/7/30 |

### Fingerprint

### Keywords

- DFT
- Hund's rule
- quantum dot
- singlet-triplet instability
- UHF

### ASJC Scopus subject areas

- Physics and Astronomy(all)

### Cite this

*AIP Conference Proceedings*(Vol. 1399, pp. 497-498) https://doi.org/10.1063/1.3666471

**Singlet-triplet ground-state instability in square quantum dot.** / Negishi, Yuki; Ishizuki, Masamu; Tsubaki, Atsushi; Takeda, Kyozaburo; Asari, Yusuke; Ohno, Takahisa.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*AIP Conference Proceedings.*vol. 1399, pp. 497-498, 30th International Conference on the Physics of Semiconductors, ICPS-30, Seoul, 10/7/25. https://doi.org/10.1063/1.3666471

}

TY - GEN

T1 - Singlet-triplet ground-state instability in square quantum dot

AU - Negishi, Yuki

AU - Ishizuki, Masamu

AU - Tsubaki, Atsushi

AU - Takeda, Kyozaburo

AU - Asari, Yusuke

AU - Ohno, Takahisa

PY - 2011

Y1 - 2011

N2 - We theoretically study the spin multiplicity in the ground state of the square quantum dot (SQD) including four electrons, and discuss a possibility of the singlet-triplet (S/T) instability in the quantum system. As predicted by Hund's rule, the ground-state triplet appears when the DQD has a point group symmetry of D 4h. This ground-state triplet is also found even in the deformed SQD (D 2h) if the confinement length L is elongated. Consequently, the S/T instability is expected along these boundary lines. It is also worthwhile to notice that the present DFT as well as UHF calculation predicts the spin-singlet ground-state when the inter-electron interaction is strengthened (larger L) even though the SQD maintains its geometrical form of D 4h. The strong electron-localization causes the destabilization in the orbital (kinetic) energies, and produces this characteristic "anti-Hund" state.

AB - We theoretically study the spin multiplicity in the ground state of the square quantum dot (SQD) including four electrons, and discuss a possibility of the singlet-triplet (S/T) instability in the quantum system. As predicted by Hund's rule, the ground-state triplet appears when the DQD has a point group symmetry of D 4h. This ground-state triplet is also found even in the deformed SQD (D 2h) if the confinement length L is elongated. Consequently, the S/T instability is expected along these boundary lines. It is also worthwhile to notice that the present DFT as well as UHF calculation predicts the spin-singlet ground-state when the inter-electron interaction is strengthened (larger L) even though the SQD maintains its geometrical form of D 4h. The strong electron-localization causes the destabilization in the orbital (kinetic) energies, and produces this characteristic "anti-Hund" state.

KW - DFT

KW - Hund's rule

KW - quantum dot

KW - singlet-triplet instability

KW - UHF

UR - http://www.scopus.com/inward/record.url?scp=84855482547&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84855482547&partnerID=8YFLogxK

U2 - 10.1063/1.3666471

DO - 10.1063/1.3666471

M3 - Conference contribution

SN - 9780735410022

VL - 1399

SP - 497

EP - 498

BT - AIP Conference Proceedings

ER -