Korotun A. Size effects in the optical absorption of low-dimensional metal systems.

The response of metal nanofilms to an electromagnetic wave is investigated and optical characteristics of the films are calculated in the framework of the density matrix formalism taking into account size oscillations of the Fermi energy. It is shown that the resonance maxima in the curves of frequency dependences shift, distance between them changes with varying the film thickness, and conductivity tensor width of the peaks is determined by dissipation mechanisms, the main ones in thin films is a scattering on a surface. Asymptotic behavior of the coefficients of absorption and transmission at high frequencies is found. Calculations were performed for Au, Ag, Al and Li. Analytical theory for the size dependence of the Fermi energy of metal nanowires is created and frequency dependences of diagonal and non-diagonal conductivity tensor components for wires of various diameters are computed using this theory. Calculations were performed for Al, Au, Cu, Nb, Li and Pb. Fundamental fact of the non-negativity of the real part of the conductivity tensor of low-dimensional metal systems at all frequencies is found while the imaginary part is an alternating function of frequency. Effect of the size quantization on absorption of electromagnetic radiation in diluted composites with metal nanoparticles of Al, Ag, Fe, Cu and Au is estimated within the modified classical theory. The part of the quantum size effect in absorption decreases with increasing dimensions of the particles and the eddy currents begin to play the dominant role. Influence of a matrix manifests itself in shift of the curve of frequency dependence without changing its character.