Charge localization and isospin blockade in vertical double quantum dots

Charge localization seems unlikely to occur in two vertically coupled symmetric quantum dots even if a small bias voltage breaks the exact isospin-symmetry of the system. However, we find a strong localization of charges in one of the dots at certain vertically applied magnetic fields. The charge localization is directly connected to ground state transitions between eigenstates differing only in parity. The transitions are driven by magnetic-field-dependent Coulomb correlations between the electrons and give rise to strong isospin blockade signatures in transport through the double-dot system.