Two-dimensional Rutherford-like scattering in ballistic nanodevices

Ballistic injection in a nanodevice is a complex process where electrons can be either transmitted or reflected, thereby introducing deviations from the otherwise quantized conductance. In this context, quantum rings (QRs) appear as model geometries: in a semiclassical view, most electrons bounce against the central QR antidot, which strongly reduces injection efficiency. Thanks to an analogy with Rutherford scattering, we show that a local partial depletion of the QR close to the edge of the antidot can counterintuitively ease ballistic electron injection. In contrast, local charge accumulation can focus the semiclassical trajectories on the hard-wall potential and strongly enhance reflection back to the lead. Scanning gate experiments on a ballistic QR and simulations of the conductance of the same device are consistent and agree that the effect is directly proportional to the ratio between the strength of the perturbation and the Fermi energy. Our observation fits the simple Rutherford formalism in two dimensions in the classical limit.