EVOLUTION OF HALF PLATEAUS AS A FUNCTION OF ELECTRIC-FIELD IN A BALLISTIC QUASI-ONE-DIMENSIONAL CONSTRICTION

We have investigated the effect of applying a dc source-drain voltage across a quasi-one-dimensional constriction formed at a GaAs-AlxGa1-xAs heterojunction. For conductances greater than 2e2/h, the measurements can be compared with the predictions of an adiabatic model proposed by Glazman and Khaetskii, in which the voltage is dropped symmetrically across the one-dimensional constriction. The source-drain voltage measurements are used to obtain the subband energies of the quasi-one-dimensional constriction. For conductances less than 2e2/h, the Glazman-Khaetskii model is no longer applicable and anomalous structure is observed.