Scattering and conductance quantization in three-dimensional metal nanocontacts

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Abstract
The transmission through three-dimenstional nanocontacts is calculated in the presence of localized scattering centers and boundary scattering using a coupled-channel recursion method. Simple confining potentials are used to investigate how robust the observation of quantized conductance is with respect to the scattering. We find that the quantum features are quite stable: the scattering by a localized scatterer will selectively smear and downshift certain quantum steps depending on the position of the scatterer, but the remaining steps will still be at integer positions. The effect of scattering by surface corrugation depends on the length scale of the corrugation. In some cases a significant downshift of the steps without accompanying smearing is observed. In general, we find that even in the cases where scattering shifts the quantum steps the quantization of the motion perpendicular to the contacts remains intact. Non-integer steps can therefore also be a signature of quantized conductance.