Plasmonic nanostructures exhibit collective oscillations of conduction electrons under optical excitation. These oscillations, known as surface plasmon resonances (SPR), result in strong electromagnetic field confinement near plasmonic nanostructures. Such confinement forms the physical basis of surface-enhanced Raman spectroscopy (SERS), field-driven charge transfer, and various nonlinear optical processes. Classical electrodynamics provides a natural and effective framework for describing these phenomena, with the field distributions and resonance behaviors well captured by macroscopic Maxwell equations embedded with dispersive dielectric functions [1,2]. 

Recent developments in spectroscopy and nanofabrication have enabled time-resolved studies of field enhancement, hot carrier dynamics, exciton diffusion, and plasmon-induced reactivity. Nonradiative plasmon decay channels can generate energetic, nonequilibrium charge carriers that interact with nearby semiconductors or molecular adsorbates. These processes are central to plasmon-driven chemistry and are increasingly investigated in both experimental and theoretical settings [3–6]. However, their microscopic mechanisms remain under debate. Open issues include the relative roles of interband and intraband transitions [7], quantum properties of surface plasmons [8], and the influence of local heating versus coherent excitation [9]. Time-resolved optical spectroscopy and single-particle studies have provided valuable insight into these dynamics [10,11], and surface-enhanced spectroscopies continue to serve as sensitive probes of molecule–plasmon coupling [12,13]. While these questions can often be addressed using classical tools, certain regimes, those involving strong coupling and vacuum fluctuations require extensions beyond semiclassical theory.

The field has begun to intersect with quantum electrodynamics (QED), where macroscopic QED offers a consistent framework for treating dissipative environments and continuous photonic modes [14,15]. This is particularly relevant for understanding molecular response in plasmonic cavities or near-metallic surfaces under quantum light fields [16,17]. As classical and quantum descriptions are increasingly applied to overlapping experimental systems, there is a pressing need to clarify their domains of validity, methodological connections, and physical implications. The workshop will bring together researchers across theoretical and experimental disciplines to examine these questions and to identify directions for bridging the existing gaps between classical plasmonics and QED-based approaches in molecular science.

References

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[12] J. P. Camden, J. A. Dieringer, J. Zhao, R. P. Van Duyne, Acc. Chem. Res., 41, 1653–1661 (2008).

[13] S. W. Bigelow, J. P. Camden, J. Phys. Chem. C, 125, 12782–12791 (2021).

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