Charge-densitywaves on metal surfaces

Abstract

Studies of the Peierls-type charge-density-wave (CDW) transitions onmetal surfaces are reviewed. After the background is reviewedbased on the theoretical and experimental works on such transitions in bulk quasi-low-dimensional materials, twoprototypical examples are presented. One is the well knownsurface reconstruction transition on W(001) and Mo(001), forwhich there was a long-standing controversy whether thetransition is due to the CDW formation or thelocal bonding. It is emphasized that these two pictures do notcontradict each other but describe the equivocal nature ofthis phenomenon. The second example is the phase transition inultrathin In films on Cu(001), which is governed by the nestingof the Fermi surface constituted by a nearly-free-electron-likesp surface resonance band, in contrast with the case of W andMo, where much-localized d-band surface resonances play a dominant role. Finally, the origin of the long-periodicitystructures widely observed in sp metals on fcc(001) systemsis discussed in terms of the Fermi-surface topology expected tobe common in these systems, which would be driven by strongelectron-phonon coupling to lead these surfaces to theformation of the peculiar long periodicities.