Asymmetries in the electron-hole pair dynamics and strong Mott pseudogap   effect in the phase diagram of cuprates
  Electron behavior in doped Mott systems continues to be a major unsolved problem in quantum many-electron physics. A central issue in understanding the universal Mott behavior in a variety of complex systems is to understand the nature of their electron-hole pair excitation modes. Using high resolution resonant inelastic x-ray scattering (RIXS) we resolve the momentum dependence of electron-hole pair excitations in two major classes of doped copper oxides which reveals a Mott pseudogap over the full Brillouin zone and over the entire phase diagram. The pair bandwidth and zone-boundary pair velocity renormalize on either sides of the phase diagram at very different rates indicating strong particle-hole doping asymmetries observed for the first time. 
M.Z. Hasan, Y. Li, D. Qian, Y.-D. Chuang, H. Eisaki, S. Uchida, Y.   Kaga, T. Sasagawa and H. Takagi