Temporal Scattering at Irremovable Exceptional Points in Lossless Drude Media

TL;DR

This paper uncovers how lossless Drude media exhibit unique temporal scattering phenomena involving static fields and exceptional points, revealing new physical insights into wave dynamics without energy loss.

Contribution

It introduces the concept of a zero-frequency flat band and exceptional line in lossless Drude media, highlighting novel static field effects during temporal scattering.

Findings

Static mode amplitude increases linearly with time.

Presence of non-propagating static fields during scattering.

Effects occur without energy violation, confirming Hermitian dynamics.

Abstract

We investigate temporal scattering in lossless Drude media and reveal an overlooked role of the zero-frequency flat band associated with static polarization charge. This flat band forms an exceptional line spanning all wavenumbers and can be directly excited during temporal scattering at photonic time interfaces, generating non-propagating static fields alongside the usual reflected and transmitted waves. Eigenvector coalescence at the corresponding exceptional points leads to two distinctive features absent in previously studied systems: a static mode whose amplitude increases linearly with time, and an additional static component arising from the system's generalized eigenvector. Remarkably, these effects occur without violating total energy conservation, underscoring the Hermitian nature of the dynamics. Our findings present a new physical picture of temporal scattering, sharply distinct from that in dispersionless and Lorentz-dispersive media.