Quantum theory of entangled-photon photoemission
Francesco Lissandrin, Bahaa E. A. Saleh, Alexander V. Sergienko, Malvin Carl Teich · Physical Review B · 2004
A quantum theory of two-photon volume photoemission from metals and semiconductors is developed when the incident source of light comprises collinear down-converted entangled-photon pairs with entanglement time ${T}_{e}.$ Despite the fact that the process involves the absorption of pairs of photons, the entangled-photon photocurrent varies linearly with the incident photon flux density. This is a consequence of the fact that the presence of one photon of an entangled-photon pair signals the presence of the other; it is in sharp contrast with the quadratic dependence of the classical two-photon photocurrent on incident photon flux density. Calculations are carried out for sodium metal (Na) and for ${\mathrm{K}}_{2}\mathrm{CsSb},$ a bialkali-antimonide semiconductor material often used as a cathode in photomultiplier tubes. The photocurrent is found to vary inversely with entanglement time although nonmonotonic behavior emerges over certain ranges of ${T}_{e}.$ Entangled-photon photoemission may well be useful for enhancing the range of two-photon photoemission spectroscopy and might find particular use in the investigation of surface and image states of various materials.