Symmetry analysis of light-induced magnetic interactions via Floquet engineering

Anisotropic magnetic interactions become the origins of intriguing magnetic structures, such as helical and skyrmion structures by the Dzyaloshinskii-Moriya interaction. In general, possible anisotropic exchange interactions are restricted by crystal symmetry. Meanwhile, by lowering the crystal symmetry with light, additional anisotropic magnetic interactions are expected according to its polarization and frequency. In this study, we clarify a relationship between anisotropic magnetic interactions and symmetry lowering in insulating magnets irradiated by light. Based on the Floquet formalism, we find that a variety of anisotropic two-spin and three-spin interactions are induced via spin-dependent electric polarizations activated by light irrespective of the presence/absence of the spatial inversion symmetry; we systematically classify them in the hexagonal point group, tetragonal point group, and their subgroups. Our symmetry analyses show that the light-induced two-spin (three-spin) interaction is owing to the reduction of the point group to a chiral point group (black and white magnetic point group). We also demonstrate the effect of the light-induced magnetic interactions on the magnetic structures in a triangular unit. Our results will be a symmetry-based reference for the Floquet engineering of magnetic structures.Comment: 15 pages, 8 figures, 7 table

NASDA knowledge-based network planning system

One of the SODS (space operation and data system) sub-systems, NP (network planning) was the first expert system used by NASDA (national space development agency of Japan) for tracking and control of satellite. The major responsibilities of the NP system are: first, the allocation of network and satellite control resources and, second, the generation of the network operation plan data (NOP) used in automated control of the stations and control center facilities. Up to now, the first task of network resource scheduling was done by network operators. NP system automatically generates schedules using its knowledge base, which contains information on satellite orbits, station availability, which computer is dedicated to which satellite, and how many stations must be available for a particular satellite pass or a certain time period. The NP system is introduced