Angle-resolved photoemission electron spectroscopy reveals a Fermi surface remnant with a d-wave like dispersion in the Mott insulator, Ca2CuO2Cl2

We report angle-resolved photoemission measurements on a Mott insulating CuO2 plane compound Ca2CuO2Cl2. This material is a parent compound to the high-Tc superconductors. We observe a loss in spectral weight of the lowest energy feature as it crosses the approximate position where band theory predicts the existence of the Fermi surface. Complimented with an analysis from metallic Bi2Sr2CaCu2O8, this suggests that the loss of spectral weight is due to the remnants of the non-interacting Fermi surface that is destroyed in the insulator. Further analysis shows a d-wave like dispersion along this ‘Fermi surface’ contour. This suggests that the d-wave like dispersion seen in the high-energy pseudogap is a remnant property of the insulator.