The in-plane photoelectric effect: A new quantum mechanism of detecting terahertz radiation in a two-dimensional electron system

We report on the discovery of a new quantum phenomenon in a 2D electron gas (2DEG) that enables efficient THz detection [1]. In this effect, electrons absorb THz photons and jump on an artificially created, electrically tunable potential step within the plane of a degenerate 2DEG. The effect is realized in a dual-gate FET-type device with two antenna-shaped gates on top of a semiconductor heterostructure. The device demonstrates a strong photoresponse, which cannot be explained by heretofore known mechanisms and which is an order of magnitude larger than expected from classical plasmonic mixing. We show that the observed photoresponse can be explained by a quantum mechanism that we call the in-plane photoelectric effect. Our theory predicts that this new mechanism is ideally suited for detection of radiation across the entire THz gap.