In this paper, we present an improved real-time current-based approach for calculating the frequency-dependent dielectric function of a bulk periodic system, which can achieve a unified treatment of longitudinal and transverse macroscopic geometries on the same footing, and an improvement to make the approach of calculating dielectric function more robust for the avoidance of numerical divergencies at low frequency near zero in some specific cases. The validity of the improved approach implementation is verified by calculating the dielectric function of bulk periodic system in the ground in the longitudinal geometry, enabling the improved approach to be extended to excited bulk periodic systems in the transverse geometry. Further, a phenomenological description of decoherence has been incorporated within the framework of time-dependent density-functional theory (TDDFT). It is concluded that the decoherence model can suppress the numerical divergence of low frequency and grows the excitonic feature of silicon, although it adopts the approximate time-dependent exchange-correlation potential. Thus, the use of the decoherence TDDFT model opens pathways for handling the decoherence effects within the framework of TDDFT.
The interaction of intense single-cycle ultrashort (0.1 to 9 fs) light pulses with diamond crystal and thin film is simulated, combining the dependent Kohn-Sham equation with the Maxwell equations. Distinct features are observed depending on the duration of the pulse. In the diamond crystal, maximum energy transfer from light pulse is observed with a pulse duration 0.3 fs. In this case, the phase of current density $J(t)$ coincides with that of the electric field $E(t)$. For the incident pulse of duration 0.1 fs, most of the light will transmit on passing the thin film. But for the pulse of duration 0.5 fs, there is more reflection than transmission. For light pulses of durations 7 and 9 fs in diamond crystal, traditional nonlinear behavior of energy transfer are observed. Interestingly, for the attosecond pulse, there is a linear scaling behavior with the pulse intensity below ${10}^{16}\phantom{\rule{4pt}{0ex}}\mathrm{W}/{\mathrm{cm}}^{2}$ on the one hand and an unusual linear dynamic interference response behavior with the pulse width, determined by the interference of the different quantum pathways, on the other hand.
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