Photoemission study of the surface state at Y on Cu(110): Band structure, electron dynamics, and surface optical properties

We report high-resolution results from the well-known "Shockley"-type surfa ce state localized around the (Y) over bar point of the Cu(110) surface Bri llouin zone. Along <(Gamma Y)over bar> the effective mass is m*/m= 0.26+/-0 .03 and the bottom of the dispersion parabola at (Y) over bar shifts linear ly with sample temperature T as E-0 = -(510+/-15)meV +(0.26+/-0.02 meV/K)T. We have also analyzed the photoemission linewidth Gamma(h) of this surface state. Our analysis results in an upper limit for the imaginary part of th e self-energy Im Sigma = Gamma(h)/2 less than or equal to( 16+/-3)meV, whic h corresponds to a photohole lifetime tau greater than or equal to(2+/-5)fs at (Y) over bar and T-->0. On the basis of recent calculations of Gamma(h) , for Cu(111) at <(Gamma)over bar> [Chulkov er al., Surf. Sci. (to be publi shed)] we interpret Gamma(h) of Cu(110) at (Y) over bar by inelastic hole-e lectron interactions, with about 50% contribution each from surface band (i n-plane) and from three-dimensional (coupling to substrate) decay channels. Finally we discuss the contribution of the (Y) over bar surface state to t he surface optical properties as observed in both second harmonic generatio n and (one-photon) reflection anisotropy spectroscopy from Cu(110).