: Light hitting a metal surface at an angle sends the electrons moving in the direction opposite to the light, a result that puzzles theorists.
Photonics en masse. Nanophotonic devices, such as these photonic chips on a silicon wafer, integrate light with electronics. Understanding light-matter interactions is essential for developing this technology, but new results clearly demonstrate that researchers don’t fully understand what happens when light hits a metal surface.
Physicists have long assumed that light hitting a metal surface at an angle pushes on the free electrons, moving them forward, yet some recent experiments show the opposite—incident light seems to pull electrons backward.
Based on new experiments, a team of researchers now offers partial clarification, at least on the experimental side. Metals in vacuum act one way, while those exposed to air behave differently, possibly because the light first interacts with molecules attached to the surface. The experiments cast doubt on researchers’ basic understanding of how light interacts with solid materials, knowledge that lies at the core of modern photonics technology...