Exotic electromagnetic scattering: near-field, far-field, and synthetic phenomena
I will discuss several recent results on electromagnetic scattering. First, I will treat free-electron radiation as near-field scattering and derive a universal upper limit to their spontaneous emission and energy loss. Such an upper limit allows us to identify a slow-electron-efficient regime of radiation operation and methods for enhancing the emission probability.
Second, I will present a general framework for nanoscale electromagnetism. The framework is featured by surface response functions known as Feibelman d-parameters, which allows a direct account of surface-related nanoscale, quantum corrections. We introduces the ‘ellipsometry’ for the surface response functions, enabled by the observation of large nonclassical spectral shifts and the breakdown of Kreibig broadening in far-field scattering measurements.
Finally, I will discuss a synthetic scattering phenomena featured by non-Abelian (non-commutative) gauge fields. Based on optical mode degeneracy, we break time-reversal symmetry in different manners to synthesize tunable non-Abelian gauge fields in real space. The interference of two final states, obtained by reversely-ordered path integrals, enables us to observe the non-Abelian Aharonov—Bohm effect with optical waves.