Metal nanofilm in strong ultrafast optical fields

We predict that a metal nanofilm subjected to an ultrashort (near-single oscillation) optical pulse of a high field amplitude greater than or similar to 3 V/A at normal incidence undergoes an ultrafast (at subcycle times less than or similar to 1 fs) transition to a state resembling semimetal. Its reflectivity is greatly reduced, while its transmissivity and the optical field inside the metal are greatly increased. Despite the metal being a centrosymmetric medium, the strong pulse causes net charge transfer in the direction determined by the carrier envelope phase (CEP) of the pulse, which is opposite to the direction of the maximum field.