Electron dynamics in CaB₆ induced by one- and two-color femtosecond laser

We simulate nonlinear electron dynamics in CaB₆ crystal within the framework of time-dependent density functional theory (TDDFT) under one-color femtosecond laser fields (400 nm, 800 nm) and two-color cases (400 nm+800 nm) with different relative phases of φ=0, φ=π/4, φ=π/2. The time-dependent Kohn-Sham equation (TDKS) is solved in real-time and real-space evolution scheme. We investigate the energy absorption and the electron excitation of CaB₆ crystal in detail. Besides, the electron density distributions and occupations are shown after each external field ends. Computational results indicate that for one-color case, the excitation behaviors are distinct due to the different frequencies; for two-color laser, we adjust the phase and obtain the asymmetric field, which causes the change of the dynamics response comparing with the symmetric field. At the end of laser, the electron occupation is broadly distributed in the energy range of 2.4-42.4 eV, which means a high excitation rate in the narrow-gap semiconductor under intense laser field. The occurrence of the breakdown is also checked for each case in the Letter.