Numerical studies of photon-based spectroscopies on high- T c superconductors

A computational algorithm with efficient scaling to tens of thousands of CPUs has been applied to large scale exact diagonalization studies of small clusters. The goal is to simulate various photon-based spectra for effective single- and multi-orbital Hubbard Hamiltonians representative of the high- T c cuprate superconductors. As an example of the utility of this method, we address the optical band gap and the spectral functions calculated from these models which strongly depend on cluster geometry and size.