Particle-hole pair excitations in a quasi-zero-dimensional Mott insulator

We investigate momentum dependence of charge excitations across the effective Mott gap in a quasi-zero dimensional (q-ZD) model cuprate Li2CuO2, using high resolution inelastic X-ray scattering by working near a resonance. In comparison to quasi-one dimensional (q-1D) systems such as Sr2CuO3 or SrCuO2, momentum dependence is much weaker in Li2CuO2. Particle-hole pair excitations at the gap edge in these low dimensional Mott systems are found to be strongly dependent on the effective dimensionality (or topology) of the lattice and the strength of electron-electron interaction.