CC BY
47LMI-I-4
Maxwell+TDDFT multiscale method for light-propagation in solids
M. Uemoto1, A. Yamada1, K. Yabana1
University of Tsukuba, Center for Computational Sciences, Tsukuba, Japan
To describe interaction between an intense laser pulse and solids, we are developing an ab-initio Maxwell+TDDFT multiscale simulation method [1]. The method combines two simulations of different spatial scales. In the microscopic scale, dynamics of electrons and ions is described using the time-dependent density functional theory (TDDFT). The time-dependent Kohn-Sham (TDKS) equation for Bloch orbitals is solved in real time using 3D Cartesian spatial grids . It describes electron dynamics in a unit cell of solids under a spatially uniform, time-dependent electric field. In the macroscopic scale, we solve the Maxwell equations, again in real time for vector potentials that describe the light propagation in solids. Both equations are solved simultaneously to describe the coupled dynamics of light propagation, electron dynamics, and atomic motion. In our simulation method, various nonlinearities in light-matter interaction can be incorporated since we solve the TDKS equation without any perturbative approximation. The descriptions of nonlinearities include x(2) and x(3) [3], saturable absorption [4], and multiphoton/tunneling ionizations [5].
In my presentation, I will show several recent applications of our method. Energy transfer from an intense laser pulse to electrons in dielectrics by multiphoton/tunneling ionization mechanisms is an important quantity to investigate the early stage of laser processing. We have compared our calculated results for SiO2 with the measurement using attosecond streaking method [6], showing that the onset of the energy transfer can be reasonably described. We have also carried out an estimation of damage threshold and crater depth from our calculation and compared them with those by a single-shot femtosecond laser pulse [7], which shows a reasonable agreement. Recently, we have extended to include microscopic ionic motion as well as electron dynamics employing the Ehrenfest molecular dynamics, namely, "Maxwell+TDDFT+MD" [2]. It can describe the generations of coherent phonon and stimulated Raman wave. We have also extended the method to three-dimensional nonlinear nano-optics, solving 3D-Maxwell equation coupled with microscopic TDDFT.
Finally, we would like to mention that our computational code is made open to public as an open source software, SALMON (Scalable Ab-initio Light-Matter simulator for Optics and Nanoscience) [8], downloadable from our website, http://salmon-tddft.jp.
References
[1] K. Yabana et.al, Phys. Rev. B (2012).
[2] M. Uemoto et al, J. Chem. Phys. 150, 094101 (2019).
[3] M. Uemoto et al, CLEO, OSA Technical Digest (online) (Optical Society of America, 2017), paper JTh2A.26.
[4] A. Yamada, K. Yabana, Euro. Phys. J. D73, 87 (2019).
[5] A. Sommer et.al, Nature 534, 86 (2016).
[6] S.A. Sato et.al, Phys. Rev. B92, 205413 (2015).
[7] A. Yamada, K. Yabana, Phys. Rev. B99, 245103 (2019).
[8] M. Noda et al. Comm. Compt. Phys. 235, 356 (2019).
