Mott state and quantum critical points in rare-earth oxypnictides RO1-xFxFeAsRO1-xFxFeAs (R=La,Sm,Nd,Pr,CeR=La,Sm,Nd,Pr,Ce)

We investigate the magnetic phase diagram of the newly discovered iron-based high temperature oxypnictide superconductors of the type RO1-xFxFeAsRO1-xFxFeAs, with rare earths R=LaR=La, Sm, Nd, Pr and Ce by means of ab initio   SGGA and SGGA+USGGA+U density functional computations. We find undoped LaOFeAs to be a Mott insulator when incorporating electronic correlations via SGGA+USGGA+U for any physically relevant value of UU. The doped compounds are according to SGGA conductors with a transition from an antiferromagnetic to a nonmagnetic state at a hole doping of concentration xc=0.075xc=0.075 for R=NdR=Nd, Pr and at electron doping xc=0.25xc=0.25 for Ce and 0.6 for Sm. Superconductivity in these rare-earth oxypnictides thus appears in the vicinity of a magnetic quantum critical point where electronic correlations are expected to play an important role because of the vicinity of a Mott insulating state at zero doping.