Non-linear conductance of a saddle-point constriction

The authors present calculations of the differential conductance, G, of a constriction, defined by a saddle-point potential in a two-dimensional electron gas, in the non-linear regime of transport as a function of Fermi energy, source-drain voltage and magnetic field. The manner in which the potential is dropped along the device is considered phenomenologically. The dependence of G on the parameters that define the potential drop is investigated, extending the model proposed by Glazman and Khaetskii. A method for measuring the sub-band energies and spin-splitting energies in a bottle-neck of the constriction is also proposed. Finally, a comparison between experimental data and theoretical calculations is presented.