Electronic states of Cu(110) investigated with angle-resolved two-photon photoemission spectroscopy

Abstract

Occupied and unoccupied electronic states of Cu(110) were investigated with angle-resolved two-photon photoemission spectroscopy with an energy resolution of 30 meV. The high energy resolution enables the individual $n$ $=$ 1 and 2 image-potential-derived structures to be distinguished. The $n$ $=$ 1 structure was 0.85 eV below ${E}_{\mathrm{vac}}$ at $\mathrm{\ensuremath{\Gamma}\ifmmode \bar{}\else \={}\fi{}}$. The effective mass of the electron for the structure was the same for both dispersions along the $\mathrm{\ensuremath{\Gamma}\ifmmode \bar{}\else \={}\fi{}}\mathrm{X\ifmmode \bar{}\else \={}\fi{}}$ and $\mathrm{\ensuremath{\Gamma}\ifmmode \bar{}\else \={}\fi{}}\mathrm{Y\ifmmode \bar{}\else \={}\fi{}}$directions within the experimental error. The $n$ $=$ 2 structure appeared in the ${L}_{{2}^{\ensuremath{'}}}$-${L}_{1}$ gap along the $\mathrm{\ensuremath{\Gamma}\ifmmode \bar{}\else \={}\fi{}}\mathrm{Y\ifmmode \bar{}\else \={}\fi{}}$ direction, and it did not appear at $\mathrm{\ensuremath{\Gamma}\ifmmode \bar{}\else \={}\fi{}}$, or along the $\mathrm{\ensuremath{\Gamma}\ifmmode \bar{}\else \={}\fi{}}\mathrm{X\ifmmode \bar{}\else \={}\fi{}}$ direction, which means that the $n$ $=$ 2 structure was strongly affected by the bulk band. In this paper, other two-photon photoemission structures and dispersions are compared with results reported in the previous literature.