Coupling and dissociation in artificial molecules

Abstract

Abstract. We show that the spin-and-space unrestricted Hartree-Fock method, in conjunction with the companion step of the restoration of spin and space symmetries via Projection Techniques (when such symmetries are broken), is able to describe the full range of couplings in two-dimensional double quantum dots, from the strong-coupling regime exhibiting delocalized molecular orbitals to the weak-coupling and dissociation regimes associated with a Generalized Valence Bond combination of atomic-type orbitals localized on the individual dots. The weak-coupling regime is always accompanied by an antiferromagnetic ordering of the spins of the individual dots. The cases of dihydrogen (H2, 2e) and dilithium (Li2, 6e) quantum dot molecules are discussed in detail. PACS

Two electrons in a strongly coupled double quantum dot: From an artificial helium atom to a hydrogen molecule

“…This theoretical problem, as well as the exact and numerical solutions mentioned above, proved relevant for a description of a Wigner molecule consisting of two electrons in a quantum dot 29,30 . 28,36,37 . The weakly coupled regime was studied analytically by the Heitler-London and Hund-Mulliken methods 2,3 .…”

Lateral diatomic two-dimensional artificial molecules: Classical transitions and quantum-mechanical counterparts

“…Both ground-state and metastable electron configurations are discussed. Discontinuous transitions from one configuration to another as a function of d are observed for Nϭ6,8,11,16,17,18,and 19. We show that the structural transitions have quantum-mechanical counterparts also in the limit of noninteracting electrons.…”

“…There is growing interest in calculating [10][11][12][13][14][15][16][17] and measuring 18 -20 the properties of coupled quantum dots. Due to the two-dimensional ͑2D͒ nature of quantum dots the twoatom system is different whether the quantum dots are coupled in the plane in which the electrons are confined ͑lat-erally coupled͒ or in the perpendicular direction ͑vertically coupled͒.…”

“…Especially for laterally coupled quantum dots only a limited number of studies have appeared. [13][14][15][16][17] Classical studies serve as a good starting point for more demanding quantum-mechanical calculations. Moreover, the study of classical electrons in vertically coupled artificial atoms has revealed interesting structural transitions in the ground-state electron configurations as a function of the distance between the atoms.…”

Theoretical studies of graphene nanoribbon quantum dot qubits

“…[17][18][19][20] This is a double-Slater-determinant approach, which takes into account the correlation effect due to charge separation and is suitable for describing diatomic molecules. In contrast, the conventional HartreeFock method, which uses factorized single-particle product states (i.e.…”