Harmonic-potential traps for indirect excitons in coupled quantum wells

We explain our method of creating an in-plane harmonic potential for indirect excitons in coupled quantum wells, which has been developed for experiments on Bose condensation of excitons in two dimensions, although this method may also be used for trapping a two-dimensional electron gas. The indirect excitons in our coupled quantum wells exhibit a Stark shift of over 60 meV and lifetime of approximately 100 ns when electric field is applied normal to the wells. The excitons also move in response to applied voltage as if they had charge, with an effective mobility of 800 ${\mathrm{cm}}^2/\mathrm{V}\mathrm{}\mathrm{s}.$ We find that the effects of screening of the electric field at high carrier density are very important for understanding the behavior of the excitons.