A real-time TDDFT study of CDW phase under femtosecond optical pulse in monolayer 2H-NbSe2*

Abstract: Intense, transient electromagnetic (EM) fields have recently emerged as an exciting alternative for driving quantum materials into new phases by selectively coupling to specific degrees of freedom, making it possible to create transient and metastable states that do not exist in equilibrium. First principles study of such driven quantum phases are now possible, thanks to the velocity-gauge implementation of real-time time-dependent density functional theory (RT-TDDFT). Ultra-fast/femtosecond laser pump and probe can reveal important information in 2D transition metal dichalcogenides many of which exhibit short time-scale complex interplay between quantum phases such as CDW, valley polarization and superconductivity. In this study, we performed RT-TDDFT calculations to study how the higher-harmonic generation (HHG) behaves in CDW and non-CDW phases of monolayer NbSe2 under different laser field intensities. We simulated frequency dependent current spectra to identify the HHG modes in NbSe2 under intense laser field.