Scanning a metallic tip close to a quantum point contact

Low-temperature transport experiments on a quantum point contact under the influence of a scanning gate are reported. The scanning gate is the metallic tip of a scanning force microscope operating at a temperature of 300 mK. In particular, the influence of the scanning tip on conductance resonances observed in the gate-characteristics of the point contact is studied. The strongest conductance resonances appear to be related to the local potential within the channel of the point contact. As a consequence, the point contact with its conductance resonances can be used as a sensor for the local tip-induced potential.