Transition of the True Ground State in a Coupled Three-Layer Quantum Dot

Low-lying states of a vertically coupled three-layer quantum-dot system are studied. Each layer contains one electron, and the tunnelling of electrons between layers is neglected. Effects of the interlayer separation d and the external magnetic field B are evaluated by numerical calculations. In the strong coupling case (i.e., d is small), as in a single dot, transitions of the angular momentum L of the true ground states occur when B increases, whereas in the weak coupling case the transition does not occur and the L remains zero. Furthermore, it is found that the variation of d may also induce the L-transition. As a result, a phase diagram of L of the true ground state is given in the d - B plane.