Standing Friedel waves: a quantum probe of electronic states in nanoscale devices

Abstract

We report a study of the dynamic response of electrons in a nanowire or a two-dimensional electron gas under a capacitively coupled ''spot gate'' driven by an AC voltage. A standing wave with wavevector equal to twice the Fermi wavevector is formed near the spot gate and near edges and boundaries, analogous to the static Friedel oscillations near defects at equilibrium. From the spatial modulation and resonance frequencies of the standing Friedel wave (SFW), electronic properties of nanoscale devices, including the Fermi velocity and eigenenergy spacings, can be measured directly.