Abstract: 

Plasmonic phenomena in metals are commonly explored within the framework of classical electrodynamics and semiclassical models for the interactions of light with free-electron matter. The more detailed understanding of mesoscopic electrodynamics at metal surfaces is, however, becoming increasingly important for both fundamental developments in quantum plasmonics [1] and potential applications in emerging light-based quantum technologies [2]. While this intuitively calls for a full quantum description of plasmon-enhanced light-matter interactions, recent discoveries suggest how classical electrodynamics may still suffice if appropriately dressed by quantum-corrected mesoscopic boundary conditions – surface-response formalism.

The colloquium will address three cases, where mesoscopic electrodynamic effects matter: 1) plasmon-emitter interactions [4], electronic surface states in crystalline materials [5], and plasmon-polariton interactions in graphene-on-metal structures [6]. Finally, prospects for probing electrodynamics of correlated electron materials are discussed [7].

[1] N.A. Mortensen, “Mesoscopic electrodynamics at metal surfaces – From quantum-corrected hydrodynamics to microscopic surface-response formalism”, Nanophotonics 10, 2563 (2021)

[2] A.I. Fernández-Domínguez, S.I. Bozhevolnyi & N.A. Mortensen, “Plasmon-enhanced generation of non-classical light”, ACS Photonics 5, 3447 (2018).

[4] P.A.D. Gonçalves et al., ”Plasmon-Emitter Interactions at the Nanoscale”,
Nat. Commun. 11, 366 (2020).

[5] A.R. Echarri et al., "Optical response of noble metal nanostructures: Quantum surface effects in crystallographic facets", Optica 8, 710 (2021)

[6] P.A.D. Gonçalves et al., Quantum Surface-Response of Metals Revealed by Acoustic Graphene Plasmons", Nat. Commun. 12, 3271 (2021)

[7] A.T. Costa et al., "Harnessing Ultra-confined Graphene Plasmons to Probe the Electrodynamics of Superconductors", PNAS 118, e2012847118 (2021)