Plasmonic and dielectric Mie resonances in subwavelength nanostructures provide an efficient way to manipulate light below the diffraction limit that has fostered the growth of plasmonics and nanophotonics. Plasmonic resonances have been mainly related with the excitation of free charge carriers, initially in metals, and dielectric Mie resonances have been identified in Si nanostructures. Remarkably, although much less studied, semi-metals, semiconductors and topological insulators of the p-block enable plasmonic resonances without free charge carriers and dielectric Mie resonances with enhanced properties compared with Si. In this review, we explain how interband transitions in these materials show a major role in this duality. We evaluate the plasmonic and Mie performance of nanostructures made of relevant p-block elements and compounds, especially Bi, and discuss their promising potential for applications ranging from switchable plasmonics and nanophotonics to energy conversion, especially photocatalysis.

We calculate, in the quasistatic coupled dipole approximation, the analytical expressions of the effective dielectric tensor of a single layer of polydisperse ellipsoidal nanoparticles with two of their principal axes in the layer's plane and embedded in a homogeneous dielectric medium. The organization (isotropic or anisotropic) and orientation (without or with a preferential in-plane orientation) of the nanoparticles is taken into account, together with their (possibly correlated) in-plane size, in-plane projected shape, and height distributions. In particular, we propose to describe the response of a layer of nanoparticles presenting a height distribution by using a vertically graded effective medium model. The expressions are tested in the case of finely characterized dielectric/silver/dielectric granular trilayers grown by means of vapor deposition in which the silver coalesced nanoparticles present correlated in-plane size and in-plane projected shape/height distributions and a moderate surface coverage of about 25%. A satisfactory quantitative agreement is obtained between the simulated and measured surface plasmon extinction bands of the metal nanoparticles. This agreement is permitted by the capability of the effective medium model of taking into account the ellipsoidal shape of the nanoparticles. The significant role of the size and shape distributions is also demonstrated.

We investigate the origin of the ultraviolet - visible plasmonic properties of three elemental materials from the p-block: Bi, Sb and Ga, which has not been discussed so far despite growing interest in these materials for plasmonic applications. We review and analyze a broad range of optically-determined dielectric functions ε = ε₁ + jε₂ of these elemental materials available in the literature, covering a wide photon energy range (from 0.03 to 24 eV). It is shown that the contribution of free carriers to ε₁ in the ultraviolet - visible is negligible for Bi and Sb and small for Ga. In contrast, the interband transitions of these elemental materials show a high oscillator strength that yields a strong negative contribution to ε₁ in the ultraviolet - visible. Therefore it is proposed that, in nanostructures made of these elemental materials, the interband transitions induce localized surface plasmon-like resonances in the ultraviolet - visible. It is examplified how these resonances are sensitive to the size and environment of the nanostructures. Furthermore, ultraviolet - visible plasmonic properties achieved through interband transitions, without free carrier excitation, are especially appealing because they might be tuned through the tailoring of the band structure and by the occupancy of electronic states. Therefore they are promising for the development of broadly tunable nanostructures and metamaterials.