Self-doped Mott insulator for parent compounds of nickelate superconductors

Motivated by analyses of the reported electrical resistivity and Hall coefficient data in the normal state, the authors propose that the parent compound of the newly discovered superconducting nickelate Nd_1-xSrₓNiO₂ is a self-doped Mott insulator, in which the low-density Nd $5d$ conduction electrons couple to localized Ni 3d_x²-y² electrons to form Kondo spin singlets at low temperature. The antiferromagnetic long-range order is suppressed and an insulator-metal transition results.