Nanocorrugation-Induced Forces between Electrically Neutral Metallic Objects

Recent advances in nanotechnology have created tremendous excitement across different disciplines, but in order to fully control and manipulate nanoscale objects, we must understand the forces at work at the nanoscale, which can be very different from those that dominate the macroscale. We show that there is a kind of curvature-induced force that acts between nanocorrugated electrically neutral metallic surfaces. Absent in flat surfaces, such a force owes its existence entirely to geometric curvature and originates from the kinetic energy associated with the electron density, which tends to make the profile of the electron density smoother than that of the ionic background and hence induces curvature-induced local charges. Such a force cannot be found using standard classical electromagnetic approaches, and we use a self-consistent hydrodynamics model as well as first-principles density functional calculations to explore the character of such forces. These two methods give qualitatively similar results. We found that the force can be attractive or repulsive, depending on the details of the nanocorrugation, and its magnitude is comparable to light-induced forces acting on plasmonic nano-objects.