Correlation between Fermi surface transformations and superconductivity   in the electron-doped high-$T_c$ superconductor Nd$_{2-x}$Ce$_x$CuO$_4$
  Two critical points have been revealed in the normal-state phase diagram of the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_4$ by exploring the Fermi surface properties of high quality single crystals by high-field magnetotransport. First, the quantitative analysis of the Shubnikov-de Haas effect shows that the weak superlattice potential responsible for the Fermi surface reconstruction in the overdoped regime extrapolates to zero at the doping level $x_c = 0.175$ corresponding to the onset of superconductivity. Second, the high-field Hall coefficient exhibits a sharp drop right below optimal doping $x_{\mathrm{opt}} = 0.145$ where the superconducting transition temperature is maximum. This drop is most likely caused by the onset of long-range antiferromagnetic ordering. Thus, the superconducting dome appears to be pinned by two critical points to the normal state phase diagram. 
T. Helm, M. V. Kartsovnik, C. Proust, B. Vignolle, C. Putzke, E.   Kampert, I. Sheikin, E.-S. Choi, J. S. Brooks, N. Bittner...
cond-mat.str-el cond-mat.supr-con