Curvature-controlled surface transport and far-infrared absorption in metallic nanoparticles

Classical quasistatic electrodynamics successfully describes electromagnetic absorption in smooth metallic nanoparticles but systematically underestimates the far-infrared absorption observed in nanoparticles possessing correlated surface morphology. We develop a phenomenological geometric–transport framework that extends the conventional quasistatic Drude–Mie description by combining two independent mechanisms: curvature-induced redistribution of the quasistatic electric field and anisotropic quasiballistic electron transport within the near-surface layer. The same geometrical framework also predicts curvature-induced localization of vortex (eddy-current) loops, providing an additional magnetic contribution to far-infrared absorption. To describe directional surface scattering, we introduce an effective surface-corrugation model characterized by two geometric scales: the local curvature radius rc and the correlation length h of the surface morphology. These scales define the dimensionless control parameters X = R/rc and Y = l0(T)/h, where R is the particle radius and l0(T) is the electronic mean free path. The resulting geometric–transport map identifies the conditions under which curvature-enhanced field localization and anisotropic surface currents act cooperatively to produce substantial surface-mediated electromagnetic dissipation, while localized vortex-current dissipation provides a complementary magnetic absorption channel. The proposed framework establishes a unified phenomenological description of morphology-controlled far-infrared absorption in metallic nanoparticles with correlated surface morphology, showing how nanoscale geometry simultaneously governs local electromagnetic-field redistribution, anisotropic surface transport, and localized vortex-current dissipation.