Influence of surface electronic structure on quantum friction between Ag(111) slabs

Abstract

The theoretical formulation developed in Phys. Rev. B 83, 205424 (2011) is applied to explore how surface electronic structure modifies the noncontact friction force between two silver slabs. We find that the friction shows three distinct regimes for different thicknesses. For very thin slabs $N=1--7$ monolayers (ML) quantum friction vs velocity shows oscillations which are due to the quantum size effect. At about $10ML$ friction rapidly increases because the surface state energies fall below ${E}_{F}$, which opens a new intraband electron-hole excitation channel. And for $N>15$ the friction is strongly enhanced due to the excitation of acoustic surface plasmons.