Magnetic-field effects on the transport coefficients of a quantum point contact

Abstract

We compute the conductance and the thermopower of a quantum point contact in a two-dimensional system under the effect of a magnetic field. We use a potential for the constriction that is abrupt along the drift direction. Different potential profiles in the transverse direction do not affect the results qualitatively. In agreement with the experiments, we find that an increasing magnetic field improves the quantization of conductance, but, in the range of fields of interest, some oscillations survive connected with the possibility of interference effects. The thermopower has oscillations that, with increasing magnetic field, beome more intense in the positive values but still have negative ones, as experimentally observed.