Spin-transitions in a triple lateral quantum dot molecule in a magnetic field

We present a theory on the effects of the magnetic field on the electronic structure and spin-transitions of lateral triple quantum dot molecule filled with a few electrons. We use a simple Hubbard model and a microscopic model based on linear combination of harmonic orbitals (LCHO) method combined with configuration interaction (CI) approach for many electron systems. It is shown that, in the presence of a magnetic field, periodic spin singlet–triplet transitions occur for two- and four-electron systems due to the Aharonov–Bohm (AB) oscillations of single-electron energy levels. This leads to the possibility of controlling the total spin of the many-electron system. For three-electron system we find a transition from a magnetically frustrated to the spin-polarized state which is a result of the competition between the Zeeman energy and the effects due to topology and Fermi statistics. We discuss the impact of these magnetic field induced phase transitions on the addition spectrum.