球電のようなテラヘルツソリトン（Ball-Lightning-like Terahertz Solitons）

The emergence of confined structures and pattern formation, such as solitons, are exceptional manifestations of nonlinear interactions found in a variety of physical, chemical, and biological systems. Although the study of stationary relativistic electromagnetic solitons holds significant potential for advancing high-energy photon storage and radiation mechanisms – as exemplified by natural phenomena such as ball lightning – harnessing these dynamics remains a formidable scientific and technical challenge. In this work, we report the first controlled generation of macroscopic static solitons that replicate the defining characteristics of ball lightning: millimeter-scale spherical morphology, 100 ns longevity in the laboratory frame (with scaling equivalence to meter-scale dimensions and second-scale duration in natural conditions), and argon-ion broadband optical emissions spanning ultraviolet to infrared spectra, marked by characteristic lines of elemental ionization processes. By leveraging field-enhanced surface plasmon polaritons in argon environments, we demonstrate relativistic-intensity confinement that spontaneously organizes into stable terahertz solitons via dynamic equilibrium between radiation pressure and plasma gradient forces. Our time-resolved experimental measurements establish a viable framework for pioneering investigations in optical soliton physics, advanced energy storage mechanisms, and the long-standing scientific enigma of ball lightning.