Energy-Level Statistics and Orbital Magnetism of Interacting Electrons in Disordered Quantum Dots

The effects of the Coulomb interaction on energy-level statistics and orbital magnetism in disordered two-dimensional quantum dots are studied within a self-consistent finite-temperature Hartree-Fock (HF) approximation. The nearest-neighbor level-spacing distribution of the HF energy at the Fermi level is shown to depend only weakly on magnetic fields. Fluctuations in the number of electrons, suppressed by a Coulomb gap produced at the Fermi energy, are also insensitive to magnetic fields. This insensitivity leads to the nonexistence of a large paramagnetism predicted for isolated mesoscopic systems of noninteracting diffusive electrons.