Charge-density waves on metal surfaces

Studies of the Peierls-type charge-density-wave (CDW) transitions on metal surfaces are reviewed. After the background is reviewed based on the theoretical and experimental works on such transitions in bulk quasi-low-dimensional materials, two prototypical examples are presented. One is the well known surface reconstruction transition on W(001) and Mo(001), for which there was a long-standing controversy whether the transition is due to the CDW formation or the local bonding. It is emphasized that these two pictures do not contradict each other but describe the equivocal nature of this phenomenon. The second example is the phase transition in ultrathin In films on Cu(001), which is governed by the nesting of the Fermi surface constituted by a nearly-free-electron-like sp surface resonance band, in contrast with the case of W and Mo, where much-localized d-band surface resonances play a dominant role. Finally, the origin of the long-periodicity structures widely observed in sp metals on fcc(001) systems is discussed in terms of the Fermi-surface topology expected to be common in these systems, which would be driven by strong electron-phonon coupling to lead these surfaces to the formation of the peculiar long periodicities.