Spin–spin interaction in artificial molecules with in-plane magnetic field

We investigate theoretically the spin–spin interaction of two-electrons in vertically coupled QDs as a function of the angle between magnetic field and growth axis. Our numerical approach is based on a real-space description of single-particle states in realistic samples and exact diagonalization of carrier–carrier Coulomb interaction. In particular, the effect of the in-plane field component on tunneling and, therefore, spin–spin interaction will be discussed; the singlet–triplet phase diagram as a function of the field strength and direction is drawn.