Vertically coupled double quantum dots in magnetic fields

Ground- and excited-state properties of vertically coupled double quantum d ots are studied by exact diagonalization. Magic-number total angular moment that minimize the total energy are found to reflect a crossover between el ectron configurations dominated by intralayer correlation and those dominat ed by interlayer correlation. The position of the crossover is governed by the strength of the interlayer electron tunneling and magnetic field. The m agic numbers should have an observable effect on the far-infrared optical-a bsorption spectrum, since Kohn's theorem [Phys. Rev. 123, 1242 (1961)] does not hold when the confinement potential is different for two dots. This is indeed confirmed here from a numerical calculation that includes Landau-le vel mixing. Our results take full account off the effect of spin degrees of freedom. A key feature is that the total spin S of the system and the magi c-number angular momentum are intimately linked because of strong electron correlation. Thus S jumps hand in hand with the total angular momentum as t he magnetic field is varied. One important consequence of this is that the spin blockade (an inhibition of single-electron tunneling) should occur in some magnetic field regions because of a spin selection rule,Owing to the f lexibility arising from the presence of both intralayer and interlayer corr elations, the spin blockade is easier to realize in double dots than in sin gle dots. [S0163-1829 (99)04408-2].