Singlet-triplet ground-state instability in square quantum dot

Yuki Negishi, Masamu Ishizuki*, Atsushi Tsubaki, Kyozaburo Takeda, Yusuke Asari, Takahisa Ohno

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution


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 languageEnglish
Title of host publicationPhysics of Semiconductors - 30th International Conference on the Physics of Semiconductors, ICPS-30
Number of pages2
Publication statusPublished - 2011
Event30th International Conference on the Physics of Semiconductors, ICPS-30 - Seoul, Korea, Republic of
Duration: 2010 Jul 252010 Jul 30

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


Conference30th International Conference on the Physics of Semiconductors, ICPS-30
Country/TerritoryKorea, Republic of


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

ASJC Scopus subject areas

  • General Physics and Astronomy


Dive into the research topics of 'Singlet-triplet ground-state instability in square quantum dot'. Together they form a unique fingerprint.

Cite this