Abstract

Plasmons –the collective electron excitations in conducting materials-- provide interesting research avenues into fundamental phenomena. They are also instrumental in applications to ultrasensitive optical detection, biosensing, spectral photometry, light harvesting, photocatalysis, quantum optics, nonlinear photonics, and metamaterials. Recent developments in this field focus on the consequences of reducing the number of electrons participating in the plasmons, thus unveiling new physics (e.g., intrinsic quantum phenomena) and generating exciting applications (e.g., light modulation and sensing at the nanoscale). Optical modes in atomically thin layers (e.g., polaritons in van der Waals materials [1], of which plasmons are a prominent example) capilize these hopes and are swiftly revealing their unprecedented optical properties, including their large electro-optical, magneto-optical, and thermo-optical responses. In this talk, I will review the state of this field and show tutorial examples of novel ultrafast and quantum-optical phenomena sustained by plasmons in atomic-scale materials, with emphasis on graphene (see Fig. 1). After a brief introduction on nanoplasmonics and a review of achievements in the field of plasmons in thin atomic layers, I will discuss the design and realistic description of a new class of random metamaterials incorporating optical gain and displaying a varied photonic behavior ranging from stable lasing to chaotic regimes [2]; a new strategy for molecular sensing that relies on the strong plasmon-driven nonlinearity of nanographenes [3]; a unique scenario in which radiative heat transfer is the fastest cooling mechanism, even beating relaxation to phonons [4]; the generation of intense high harmonics from graphene, assisted by its plasmons [5]; and the possibility of realizing order-one fast light modulation in ultrathin metal-graphene films. I will conclude by discussing the potential of these phenomena for the implementation of quantum-optics devices in a robust solid-state environment under ambient conditions.

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