Quantum pathways interference in photoemission from metals induced by two-color lasers with a dc bias

Coherent control of photoemission from metals by two-color lasers has drawn great interest for its flexibility in manipulating ultrafast electron dynamics. Here, we analyze the quantum pathways interference in two-color laser induced photoemission, using an exact analytical solution of the time-dependent Schrödinger equation [1,2]. The theory includes contributions from all possible quantum pathways and interferences among them. Effects of laser and dc bias fields on the weight of each pathway and the interference terms are studied. Increasing the intensity ratio of the second harmonic to fundamental lasers results in more contribution from multicolor pathway and the single-color pathway of absorption of 2ω-photons, and therefore stronger interference between them and increased visibility >95%. Increasing bias voltages shifts the dominant emission to processes with fewer photon absorption, which sequentially decreases the interference between the ω- and the 2ω-pathways, and between single-color and multicolor pathways. Our study provides insights into the underlying physics of coherent control of two-color photoemission.