Ultrafast strong-field photoelectron emission due to two-color laser fields

Electron emission from solids driven by two-color lasers provides great flexibility for the control of electron dynamics in ultrashort spatiotemporal scales due to the interference effect. Here, we construct an analytical model for the highly nonlinear photoelectron emission from a metal surface illuminated by two-color laser fields, by solving the time-dependent Schrodinger equation. The exact solution is valid for arbitrary harmonic orders, laser intensities, phase difference between two lasers, and metal work function and Fermi level. We find two-color lasers can strongly modulate both the electron energy spectra and the emission current up to 99%. Using the same input parameters, our theoretical prediction for the photoemission current modulation depth (93.9%) is almost identical to the experimental result (94%) in [M. Forster et al., Phys. Rev. Lett. 117, 217601 (2016)].