Platform for Light-Matter Interaction Simulation: SALMON

Tomohito Otobe

Kansai Institute for Photon Science, QST, Japan

The interaction of light and matter is becoming even more important. The advantage of light, especially lasers, is that it can be made infinitely strong and short. It is only with lasers, which are coherent boson beams, that nonlinear effects can be observed at extremely short times (in attoseconds). The understanding of light and matter interaction has progressed separately while being interrelated. In the optical sciences, the properties of matter have been confined to optical constants based on Maxwell's equations. On the other hand, in materials science, the understanding of electronic states has been based on Schrodinger's equation (density functional theory = DFT), and light has been treated as a perturbation of the state in frequency-domain time-dependent density functional theory (TDDFT).

We first proposed an adaptation of TDDFT to the nonlinear optical response of solids [1] and subsequently developed a new computational method that fuses the Maxwell equations with TDDFT [2]. This method was released as an open-source program SALMON [3] and is mainly operated by KPSI. Recently, we have extended the functionality of SALMON by introducing spin-orbit coupling, reducing the computational complexity by using the semiconductor Bloch equation, and clarifying the initial process of laser processing.

KPSI also attempts to extend the computable phenomena by changing the electronic dynamics description part, such as Maxwell+VDDFT, Maxwell+Vlasov [4], and Maxwell+temperature model [5], in addition to Maxwell+TDDFT. In this talk, I will discuss the current status of SALMON and simulations of light-matter interactions using methods other than SALMON.

[1] T. Otobe, et. al., Phys. Rev. B 77, 165104 (2008)

[2] K. Yabana, T. Sugiyama, Y. Shinohara, T. Otobe, and G. F. Bertsch, Phys. Rev. B 85, 045134 (2012)

[3] M. Noda, et. al., Comput. Phys. Commun. 235, 356 (2019)

[4] M. Tani, T. Otobe, Y. Shinohara, and K. L. Ishikawa, Phys. Rev. B 104, 075157 (2021)

[5] P. Venkat and T. Otobe, APEX 15, 041008 (2022)

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