Singlet-triplet avoided crossings and effective $g$ factor versus spatial orientation of spin-orbit-coupled quantum dots

Abstract

We study avoided crossings opened by spin-orbit interaction in the energy spectra of one- and two-electron anisotropic quantum dots in perpendicular magnetic field. We find that for simultaneously present Rashba and Dresselhaus interactions the width of avoided crossings and the effective $g$ factor depend on the dot orientation within (001) crystal plane. The extreme values of these quantities are obtained for [110] and [1$\bar{1}$0] orientations of the dot. The width of singlet-triplet avoided crossing changes between these two orientations by as much as two orders of magnitude. The discussed modulation results from orientation-dependent strength of the Zeeman interaction which tends to polarize the spins in the direction of the external magnetic field and thus remove the spin-orbit coupling effects.