Modeling AC electronic transport through a two-dimensional quantum point contact

We present new results on the a.c. transport of electrons moving through a two-dimensional (2D) semiconductor quantum point contact (QPC). We concentr ate our attention on the characteristic properties of the high frequency ad mittance (omega approximate to 0 - 50 GHz), and on the oscillations of the admittance in the vicinity of the separatrix (when a channel opens or close s), in presence of the relaxation effects. The experimental verification of these oscillations in the admittance would be a strong confirmation of our semi-classical approach to a.c. transport through a QPC, in the separatrix region.