Resonant electron–phonon coupled responses to single-shot driver : Ab initio TDDFT study of diamond

Abstract

Electronic and structural response of diamond to the single-cycle linear and circular time-dependent displacement pumping are modeled through ab initio dynamics of electrons in the framework of the time-dependent density functional theory. Here, we take diamond as a prototypical crystal with a non-zero non-diagonal component of Raman tensor, of which the force profiles generated during vibrational excitation are analyzed in terms of two adjustable parameters: amplitude and frequency of deformations. As the intensity of sub-cycle distortion pumping reaches a strongly coupled nonlinear regime, the system converts into a non-equilibrium state via distinct non-thermal pathways, involving transient modification of energy landscape transient via breaking of time-reversal and inversion symmetries. The excited charge is highly sensitive to the phase of the driving field but remains largely independent of its frequency. Enhanced nonlinear lattice vibrations generate coherent phonons and lead to the emergence of squeezed phonon states in both linear and circular pumping. This study may open the avenue for understanding and control of hidden phases of solid states, which are not accessible through heating or other conventional thermodynamics, but can be accessed only via dynamical modification of coupling strength.