Nonequilibrium Band Mapping of Unoccupied Bulk States Below the Vacuum Level by Two-Photon Photoemission

ORAL

Abstract

We demonstrate two-photon photoemission (2PPE) to map a bulk unoccupied band, \textit{viz.} the Cu \textit{sp}-band 0 to 1 eV below the vacuum level, in the vicinity of the L point. This short-lived bulk band is seen due to the strong optical pump rate, and the observed transition energies and their dispersion with photon energy, are in excellent agreement with tight-binding band-structure calculations. A careful analysis of the 2PPE spectra permits unambiguous assignment of the transitions. The variation of the 2PPE final-state energy with photon energy has a measured slope of $\sim $1.64, in contrast with values 1 or 2 observed for 2PPE from two-dimensional states, i.e., image and surface states.

*This research was supported by DOE, Contract Nos. DE-FG 02-04-ER-46157 and DE-AC 02-98-CH-10886.

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Authors

  • Jerry I. Dadap

    • Columbia University, New York, NY

  • Zhaofeng Hao

    • Columbia University, New York, NY

  • Kevin R. Knox

    • Columbia University, New York, NY

  • Mehmet Yilmaz

    • Columbia University, New York, NY
    • Columbia University

  • Nader Zaki

    • Columbia University, New York, NY

  • Richard Osgood

    • Columbia University, New York, NY
    • Columbia University

  • Peter Johnson

    • Brookhaven National Laboratory, Upton, NY
    • BNL
    • Brookhaven National Laboratory
    • Brookhaven National Lab
    • Brookaven National Laboratory