Charge correlation and spin coupling in double quantum dots

Abstract

We study both the spin and the charge correlations between two electrons in vertically coupled quantum dots with a finite well width, using a diffusion quantum Monte Carlo method. We clarify the mechanism of their dependence on both a barrier thickness and a magnetic field. When the barrier thickness increases, two‐electron occupation probability in the same dot is suppressed drastically by enhanced charge correlation relative to the electron transfer effect and a magnitude of the antiferromagnetic spin coupling decreases in two stages, from a strong coupling to a weak coupling. As the magnetic field increases, both the antiferromagnetic spin coupling constant and the two‐electron occupation probability in the same dot are suppressed. In the case of weak lateral confinement, transitions of the ground state can be also induced by a magnetic field and they accompany changes of the spin coupling between antiferromagnetic and ferromagnetic couplings.