Fluctuation of conductance-peak spacings in large semiconductor quantum dots

Fluctuation of Coulomb blockade peak spacings in large two-dimensional semiconductor quantum dots is studied within a model based on the electrostatics of several electron islands among which there are random inductive and capacitive couplings. Each island can accommodate electrons on quantum orbitals whose energies depend also on an external magnetic field. In contrast with a single-island quantum dot, where the spacing distribution is close to Gaussian, here the distribution has a peak at small spacing value. The fluctuations are mainly due to charging effects. The model can explain the occasional occurrence of couples or even triples of closely spaced Coulomb-blockade peaks, as well as the qualitative behavior of peak positions with the applied magnetic field.