XVIth International Workshop on Quantum Systems in Chemistry and Physics 

Abstract 
Development of FirstPrinciples Maxwell+TDDFT MultiScale Simulator for
Propagation of HighIntensity Laser Pulse 
Takeru Sugiyama^{1},Yasushi Shinohara^{1},Tomohito Otobe^{2},Kazuhiro Yabana^{1,3} and George F. Bertsch^{4}
^{1}Graduate School for Pure and Applied Sciences, University of Tsukuba, Japan
^{2}Center for Computational Sciences, University of Tsukuba, Japan
^{3}Advanced Photon Research Center, Japan Atomic Energy Agency, Japan
^{4}Department of Physics, University of Washington, USA 
Interaction between light and matter is described by the Schroedinger and Maxwell equations. The Schroedinger equation describes electron dynamics while the Maxwell equation describes propagation of electromagnetic fields. For ordinary weak lightwave, one can apply the perturbation theory for the Schroedinger equation which decouples two equations with the dielectric function. However, for intensive laser pulses, one cannot separate them because of the nonlinear electron responses to the strong electric field of the laser pulse. Previously, we developed a framework in TDDFT to describe electron dynamics under spatiallyuniform timevarying electric field solving the timedependent KohnSham equation in realtime [1,2]. We now extend it to a firstprinciples simulator calculating simultaneously the coupled nonlinear dynamics of electrons and electromagnetic field. Since the lengthscale is much different between the laser wavelength (μm) and the electron dynamics (nm), we employ two different spatial grids and express the vector potential in the macroscopic grids and the KohnSham orbitals in the microscopic grids. As a preliminary demonstration, we will show our calculation for the one dimensional propagation of electromagnetic field incident on bulk Si.
[1]T. Otobe et al. Phys.Rev.B77,165104(2008)
[2]Y. Shinohara et al. Phys.Rev.B82,155110(2010)

Figure. Laser pulse irradiated on bulk Si surface. The intensity and the frequency of the laser pulse is set to I=5×10^{12}W/cm^{2} and ℏw=1.55eV (below calculated bandgap, 2.4eV), respectively. The upper panels show propagation of electromagnetic field. The lower panels show the groundstate electron density (left) and the density change of electrons from that in the ground state at the surface (middle and right).



