Ab-initio study of surface plasmons on palladium surfaces

Collective electronic excitations at metal surfaces lead to strongly localized electromagnetic fields that play a key role in numerous phenomena in physics, material science, biology or medicine [1]. In particular, surface plasmons are modes that appear in vacuum/metal boundaries, with a constant dispersion relation in the long-wavelength limit predicted by simple models [2]. However, in real metallic systems such predictions often fail. In particular, in many materials, when the non-local behavior of the electronic response is considered, additional collective modes characterized by significantly lower frequencies may appear [3]. In this work, we perform first-principles time-dependent density-functional calculations of the excitation spectra of the palladium surfaces, in order to establish the characteristics of its surface plasmons. We analyze the properties of the surface collective excitations using the surface response function, which is closely related to the permittivity of the material. Our results thus contribute to gaining a better understanding of the optical response of palladium structures.
[1] J. M. Pitarke et al., Rep. Prog. Phys. 70, 1 (2006).
[2] R. H. Ritchie, Phys. Rev. 106, 874 (1957).
[3] V. M. Silkin et al., Phys. Rev. B 80, 245114 (2009).