The electronic structure of Mott insulators continues to be a major unsolved problem in physics despite more than half-century of intense research efforts. Well-developed momentum-resolved spectroscopies such as photoemission or neutron scattering cannot probe the full Mott gap. We report observation of dispersive charge excitations across the Mott gap in a high Tc parent cuprate Ca2CuO2Cl2 using high resolution resonant inelastic x-ray scattering shedding light on the anisotropy of Mott-gap. The results provide direct support for the Hubbard model to describe charge excitations across the Mott gap.
@article{arxiv.cond-mat/0102489,
title = {Electronic Structure of Mott Insulators Studied by Inelastic X-ray Scattering},
author = {M. Z. Hasan and E. D. Isaacs and Z-X. Shen and L. L. Miller and K. Tsutsui and T. Tohyama and S. Maekawa},
journal= {arXiv preprint arXiv:cond-mat/0102489},
year = {2009}
}