Low-lying energies for two electrons in the type-II quantum dot, as a function of the magnetic flux Φ. Solid and dash lines indicate spin-singlet and triplet, respectively. The ratio of the dot radius R to the effective Bohr radius a
B = 4πϵħ
2 is (a) 0.01, (b) 0.1, (c) 1, and (d) 10. The ground-state energy oscillates by the period of h/2e for R/a
B ≳ 1.