Quantum Critical Point in Electron-Doped Cuprates

We analyze doping dependent spectral intensities and Fermi surface maps obtained recently in Nd${}_{2-x}$Ce${}_x$CuO${}_{4\pm \delta }$ (NCCO) via high resolution ARPES measurements, and show that the behavior of this electron-doped compound can be understood as the closing of a Mott (pseudo) gap, leading to a quantum critical point just above optimal doping. The doping dependence of the effective Hubbard $U$ adduced by comparing theoretical and experimental spectra is in resonable accord with various estimates and a simple screening calculation.