Observation of charge redistribution during bond formation in one-dimensional alkali-metal wires

We have tracked the formation of Li wires in the Li/Cu(100) system. Wire formation is driven by the increased in-plane adatom density as Li coverage increases from 0.5 to 0.6 Monolayers (ML). We used a combination of Helium Atom Scattering (HAS) and Density Functional Theory (DFT) to show the emergence of anisotropic, 1-dimensional inter-Li bonding. HAS, which is sensitive to the outermost electronic charge density, shows a transition to an unexpectedly large, 1-dimensional electronic corrugation at a coverage of 0.6ML. DFT calculations identify the corrugation as the formation of a corrugated array of Li wires. Bond formation along the Li wires is enabled by charge donation from the substrate but without significant change to the layer spacing.