Double quantum dot with two electrons: Singlet-triplet transitions - art. no. 085332

The magnetic character of the ground state of two electrons on a double qua ntum dot, connected in series to left and right single-channel leads, is co nsidered. By solving exactly for the spectrum of the two interacting electr ons, it is found that the coupling to the continuum of propagating states o n the leads, in conjunction with the electron-electron interactions, may re sult in a delocalization of the bound state of the two electrons. This, in turn, reduces significantly the range of the Coulomb interaction parameters over which singlet-triplet transitions can be realized. It is also found t hat the coupling to the leads favors the singlet ground stale.