  In connection with the experiment on oxygen isotope effect of Bi2Sr2CaCu2O8
with the angle-resolved photoemission spectroscopy (ARPES), we theoretically
study the isotope-induced band shift in ARPES by the Hartree-Fork and quantum
Monte Carlo methods. We find that this band shift can be clarified based on a
quadratically coupled electron-phonon (e-ph) model. The large ratio of band
shift versus phonon energy change is connected with the softening effect of
phonon, and the positive-negative sign change is due to the momentum dependence
of the e-ph coupling.
