ANALYTICAL MODEL OF A ONE-DIMENSIONAL CONSTRICTION WITH MANY OCCUPIED SUBBANDS - CALCULATION AND EXPERIMENT

We have measured the differential conductance of two different one-dimensional (1D) constrictions with several occupied subbands at low temperature under conditions of high dc source-drain bias relative to the 1D subband spacing. The results are compared with a simulation based on a saddle-point potential with and without a thin equipotential strip at the center. We fit the experimental results at high conductance by increasing the width of the equipotential strip with an increase in number of conducting subbands. For a split gate where the depth of the electron gas is 70 nm and where there are at most three occupied 1D subbands, a simple parabolic saddle-point model is sufficient. For a device where the depth of the electron gas is 27 nm and there are eight occupied 1D subbands, the modified potential model is needed to give good agreement with experimental data.