Real‐time, real‐space implementation of the linear response time‐dependent density‐functional theory

We apply the coupled dynamics of time-dependent density functional theory and Maxwell equations to the interaction of intense laser pulses with crystalline silicon. As a function of electromagnetic field intensity, we see several regions in the response. At the lowest intensities, the pulse is reflected and transmitted in accord with the dielectric response, and the characteristics of the energy deposition is consistent with two-photon absorption. The absorption process begins to deviate from that at laser intensities ∼ 10 13 W/cm 2 , where the energy deposited is of the order of 1 eV per atom. Changes in the reflectivity are seen as a function of intensity. When it passes a threshold of about 3 × 10 12 W/cm 2 , there is a small decrease. At higher intensities, above 2 × 10 13 W/cm 2 , the reflectivity increases strongly. This behavior can be understood qualitatively in a model treating the excited electron-hole pairs as a plasma.

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“…The wave functions are evolved by using the 4-th order expansion of the TDDFT evolution operator 37,38 …”

Section: B Electronic Scalementioning

confidence: 99%

“…We employ a third order polynomial for it 38 . The dielectric function may be obtained from the conductivity by Eq.…”

Section: Appendixmentioning

confidence: 99%

Time-dependent density functional theory for strong electromagnetic fields in crystalline solids

et al. 2012

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“…Our calculation method has been described in detail elsewhere [18,21,[23][24][25], so we only provide here the details germane to our study here. The electrons dynamics is calculated using the TDKS equation,…”

Section: A Calculation Of Electron Dynamicsmentioning

confidence: 99%

“…[ 23,24] for details. The electron-electron interaction in the TDKS Hamiltonian is modeled in a simple a adiabatic local density approximation [26].…”

Section: A Calculation Of Electron Dynamicsmentioning

confidence: 99%

Numerical pump-probe experiments of laser-excited silicon in nonequilibrium phase

et al. 2014

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We calculate the dielectric response of crystalline silicon following irradiation by a high-intensity laser pulse, modeling the dynamics by time-dependent density functional theory (TDDFT). The pump-probe measurements are numerically simulated by solving the time-dependent Kohn-Sham equation with the pump and probe fields included as external fields. As expected, the excited silicon shows features of a particle-hole plasma in its response. We compare the calculated response with a thermal model and with a simple Drude model. The thermal model requires only a static DFT calculation to prepare electronically excited matter and agrees rather well with the TDDFT for the same particle-hole density. The Drude model with two fitted parameters (electron effective mass and collision time) also shows fair agreement at the lower excitation energies; the fitted effective masses are consistent with carrier-band dispersions. The extracted Drude lifetimes range from 6 fs at weak pumping fields to much lower values at high fields. However, we find that the Drude model does not give a good fit to the imaginary dielectric function at the highest fields. Comparing the thermal model with the Drude, we find that the extracted lifetimes are in the same range, 1-13 fs depending on the temperature. These short Drude lifetimes show that strong damping is possible in the TDDFT, despite the absence of electron scattering. One significant difference between the TDDFT response and the other models is that the response to the probe pulse depends on the polarization of the pump pulse. We also find that the imaginary part of the dielectric function can be negative, particularly for the parallel polarization of pump and probe fields.

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“…[9]. An important difference from other TDDFT codes is the orbital representation in 3-dimensional See the Appendix for details.…”

Section: Computational Aspectsmentioning

confidence: 99%

Magnetic circular dichroism in real-time time-dependent density functional theory

Lee

Yabana

Bertsch

2011

The Journal of Chemical Physics

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We apply the adiabatic time-dependent density functional theory to magnetic circular dichroism (MCD) spectra using the real-space, real-time computational method. The standard formulas for the MCD response and its A and B terms are derived from the observables in the timedependent wave function. We find real time method is well suited for calculating the overall spectrum, particularly at higher excitation energies where individual excited states are numerous and overlapping. The MCD sum rules are derived and intepreted in the real-time formalism; we find that they are very useful for normalization purposes and assessing the accuracy of the theory.The method is applied to MCD spectrum of C 60 using the adiabatic energy functional from the local density approximation. The theory correctly predicts the signs of the A and B terms for the lowest allowed excitations. However, the magnitudes of the terms only show qualitative agreement with experiment.

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Real‐time, real‐space implementation of the linear response time‐dependent density‐functional theory

Cited by 222 publications

References 47 publications

Time-dependent density functional theory for strong electromagnetic fields in crystalline solids

Time-dependent density functional theory for strong electromagnetic fields in crystalline solids

Numerical pump-probe experiments of laser-excited silicon in nonequilibrium phase

Magnetic circular dichroism in real-time time-dependent density functional theory

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