Theory of isotope dependence of photoemission spectra of high-T_c superconducting cuprates

We investigate the effect of isotope substitution on the electronic spectral functions within a model where the charge carriers are coupled to bosonic charge-order (CO) fluctuations centered around some mean frequency ω₀ and with enhanced scattering at wave vector q_c. It is shown that the mass dependence of ω₀ is not sufficient to account, especially at high energies, for the dispersion shifts experimentally observed in an optimally doped superconducting cuprate. Our analysis rather suggests that isotope substitution induces a change of the spatial CO correlations which gives a good account of the experimental data.