Quantum corrections in the optical properties of three-dimensional plasmonic metamaterials with subnanometer gaps

•First theoretical study of the effect of charge tunneling in 3D periodic plasmonic metamaterials.•Case study: square array of nanorods containing periodically repeated slits of subnanometer size.•The inclusion of charge tunneling induces large red shifts and widening into the observed surface-plasmon peaks and cannot be neglected in standard EM simulations.•Theory can be confirmed experimentally with standard optical setups such those of light-transmission experiments.

We study the effect of the electron tunnelling between two metallic surfaces in the optical response of a three-dimensional plasmonic metamaterial design, namely a square lattice of nanorods containing periodically repeated subnanometer slits. We show, in particular, that due to the interaction of the slits primarily within a single nanorod, the presence of charge tunnelling can modify drastically the surface-plasmon absorbance spectra in the manner of sizeable wavelength shifts and widening of the corresponding peaks, under suitable conditions of light incidence. Our calculations are based on rigorous electrodynamic multiple-scattering calculations incorporating a recently proposed quantum-corrected model [R. Esteban et al., Nat. Commun. 3, (2012) 825] simulating the effect of charge tunnelling between metal surfaces.