Ballistic transport through a quantum point contact: Elastic scattering by impurities

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Abstract
The effects of elastic scattering due to impurities in a quasi-one-dimensional constriction are investigated with an exact calculation of the conductance. It is found that the quantization of conductance is distorted owing to scattering by a single impurity which exists in an infinite constriction. The extent of deviation from quantized values depends on the strength, position, and lateral range of the scattering potential. The resonance structure due to interference of current-carrying waves is still apparent for a constriction of finite length containing an impurity. However, both the magnitude and position of these oscillations in the resonance structure are affected as a result of elastic scattering. A resonant tunneling effect is found due to a state bound to the attractive impurity potential.