AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS-ThP

Paper SS-ThP1
Photon-Induced Localization and Correlation Effects in Optically Absorbing Materials

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: D.E. Aspnes, North Carolina State University
Authors: D.E. Aspnes, North Carolina State University
L. Mantese, University of Texas, Austin
K.A. Bell, North Carolina State University
U. Rossow, Technical University of Ilmenau, Germany
Correspondent: Click to Email
Surface-optical data that contain structures related to energy derivatives of bulk critical points show that photons themselves modify the optical properties of the material being measured, and therefore, that the standard picture of optical absorption must be revised. Using a simple model that retains correlations discarded in the random phase approximation yet can be solved analytically to first order in time-dependent perturbation theory, we show that (1) the final electron and hole states are localized near the surface by the finite penetration depth of the photons but (2) these final-state packets also evolve by propagation with their respective group velocities. More important, since the energy of a wave function is the expectation value of the Hamiltonian, for finite packets the surface contribution to the energy and lifetime is also finite, thereby providing a natural explanation to derivative structures and to apparent differences in nominally bulk critical point energies and broadening parameters with surface preparation. Further, we show that (3) broadening must be described by a sinc function as in standard filter theory, instead of the traditional phenomenological broadening parameter. The implications are extensive. For example, these results show that (4) slab calculations of surface electronic properties, where limited spatial extent is an unwelcome consequence of limited computing power, may actually provide a more accurate representation of surface optical spectra than hypothetical calculations that take the entire bulk into account.