High energy anomaly in hole- and electron-doped cuprates

Recent ARPES experiments reveal the presence of a dispersion anomaly in the high $T_{c}$ cuprates. This universal anomaly appears at an energy of $\sim 300$ meV in hole-doped compounds, with a similar feature reported in the half-filled parent insulators. New experiments on Nd$_{2-x}$Ce$_{x}$CuO$_{4}$ also reveal an anomaly, but at a higher energy scale of $\sim 500$ - $600$ meV. A key question concerns the origin of this anomaly. Quantum Monte Carlo simulations of the single-band Hubbard model reveal qualitative and quantitative agreement with the dispersion anomaly throughout the doping spectrum. They demonstrate that strong correlations play a key role in the development of the anomaly as well as that of spectral weight transfers that accompany doping.