Light-matter interactions simulated on the world's fastest supercomputer


Date:
January 7, 2022
Source:
University of Tsukuba
Summary:
Researchers have developed a computational approach for simulating
interactions between matter and light at the atomic scale. The
team tested their method by modeling light -- matter interactions
in a thin film of amorphous silicon dioxide, composed of more than
10,000 atoms, using the world's fastest supercomputer, Fugaku. The
proposed approach is highly efficient and could be used to study
a wide range of phenomena in nanoscale optics and photonics.



FULL STORY ========================================================================== Light-matter interactions form the basis of many important
technologies, including lasers, light-emitting diodes (LEDs), and
atomic clocks. However, usual computational approaches for modeling such interactions have limited usefulness and capability. Now, researchers
from Japan have developed a technique that overcomes these limitations.


==========================================================================
In a study published this month in TheInternational Journal of High
Performance Computing Applications, a research team led by the University
of Tsukuba describes a highly efficient method for simulating light-matter interactions at the atomic scale.

What makes these interactions so difficult to simulate? One reason is
that phenomena associated with the interactions encompass many areas of physics, involving both the propagation of light waves and the dynamics
of electrons and ions in matter. Another reason is that such phenomena
can cover a wide range of length and time scales.

Given the multiphysics and multiscale nature of the problem, light-matter interactions are typically modeled using two separate computational
methods.

The first is electromagnetic analysis, whereby the electromagnetic fields
of the light are studied; the second is a quantum-mechanical calculation
of the optical properties of the matter. But these methods assume that
the electromagnetic fields are weak and that there is a difference in
the length scale.

"Our approach provides a unified and improved way to simulate light-matter interactions," says senior author of the study Professor Kazuhiro
Yabana. "We achieve this feat by simultaneously solving three key
physics equations: the Maxwell equation for the electromagnetic fields,
the time-dependent Kohn-Sham equation for the electrons, and the Newton equation for the ions." The researchers implemented the method in their in-house software SALMON (Scalable Ab initio Light-Matter simulator for
Optics and Nanoscience), and they thoroughly optimized the simulation
computer code to maximize its performance. They then tested the code by modeling light-matter interactions in a thin film of amorphous silicon
dioxide, composed of more than 10,000 atoms.

This simulation was carried out using almost 28,000 nodes of the fastest supercomputer in the world, Fugaku, at the RIKEN Center for Computational Science in Kobe, Japan.

"We found that our code is extremely efficient, achieving the goal of
one second per time step of the calculation that is needed for practical applications," says Professor Yabana. "The performance is close to its
maximum possible value, set by the bandwidth of the computer memory,
and the code has the desirable property of excellent weak scalability." Although the team simulated light-matter interactions in a thin film
in this work, their approach could be used to explore many phenomena in nanoscale optics and photonics.

========================================================================== Story Source: Materials provided by University_of_Tsukuba. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Yuta Hirokawa, Atsushi Yamada, Shunsuke Yamada, Masashi Noda,
Mitsuharu
Uemoto, Taisuke Boku, Kazuhiro Yabana. Large-scale ab initio
simulation of light-matter interaction at the atomic scale in
Fugaku. The International Journal of High Performance Computing
Applications, 2022; 109434202110657 DOI: 10.1177/10943420211065723 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220107101011.htm
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