Dipole polarizability of time-varying particles

Abstract Invariance under time translation (or stationarity) is probably one of the most important assumptions made when investigating electromagnetic phenomena. Breaking this assumption expected to open up novel possibilities and result in exceeding conventional limitations. However, explore field time-varying structures, we primarily need contemplate fundamental principles concepts from a nonstationarity perspective. Here, revisit those key concepts: polarizability small particle, assuming that its properties vary time. We describe creation induced dipole moment by external fields nonstationary, causal way, introduce complex-valued function, called temporal complex polarizability, for elucidating nonstationary Hertzian time-harmonic illumination. This approach can be extended any subwavelength particle exhibiting electric response. In addition, also study classical model an oscillating electron using equation motion whose damping coefficient natural frequency are changing Next, theoretically derive effective permittivity corresponding media (comprising free or bound electrons, dipolar meta-atoms) explicitly show differences with macroscopic Drude–Lorentz model. paper will hopefully pave road towards better understanding scattering particles homogenization materials, metamaterials, metasurfaces.