Observation of resonant photon drag in a two-dimensional electron gas

We observe a photon-drag voltage along the optical path of photons propagating in the plane of an unbiased 2D electron gas in GaAs quantum wells. This voltage is induced by momentum transfer from 10-μm-wavelength photons to the electrons, resonantly matched in their intersubband energy to the photons by appropriate choice of the 3.2-nm well width. The voltage is reversed when the propagation direction of the photons is reversed. Moreover, the sign of the voltage also changes by sweeping the photon energy through the intersubband resonance condition in agreement with current theory.