Shape effects on conductance quantization in three-dimensional nanowires: Hard versus soft potentials

Effects of the shapes of the cross sections of three-dimensional nanowires on electronic conductance quantization are studied for both hard- and soft-wall potentials. In both models the quantum conductance is determined by both the area and shape of the narrowmost part of the nanowire. For the hard-wall potential the semiclassical (Weyl) correction to the Sharvin formula provides an adequate approximation to the average quantized conductance. For nanowires modeled by soft-wall potentials, the average quantum conductance may be well estimated using a classical approximation.