Fig. 1: Correlation-temperature phase diagram of LaNiO₂.

a shows the correlation-temperature (U–T) phase diagram where the boundaries of various electronic phases were determined from the fits of the calculated local magnetic susceptibility (χ_loc) for the nickel d electrons, and scattering rate (Σ) for the electrons in the nickel \({d}_{{x}^{2}-{y}^{2}}\) orbital. The susceptibility values and the corresponding error bars represent the mean and the standard deviation obtained from the last few converged iterations (usually 5) for each given calculation. The red (T_CW) and green (T^*) dashed lines denote the Curie–Weiss and Fermi liquid phase boundaries, respectively. The boundary (black dashed curve, T_AFM) of the antiferromagnetic (AFM) phase was obtained by computing the temperature dependence of the magnetic order parameter, described in the text. The inset shows the U dependence of the local effective moment μ_eff, where the dashed line is a guide to the eye. b shows the low-temperature region of the U–T phase diagram, showing the regions of partially screened and fully screened (below T_FLFS) Fermi liquid phases. c shows the temperature dependence of the calculated χ_loc for the Ni-d electrons for U = 7 eV and J = 1 eV. d, e show χ_loc with the focus on the low- and high- temperature ranges, respectively. The solid line represents the best fit with the Curie–Weiss–Wilson formula \({\chi }_{loc}=\frac{C{\mu }_{eff}^{2}}{(T+\sqrt{2}{T}^{* })}\) as explained in the text. From d, e, we observe that T^* and T_CW corresponds to the temperatures where χ_loc shows deviations from the Curie–Weiss behavior. f shows the temperature dependence of the calculated scattering rate (Σ) for the electrons in the Ni \({d}_{{x}^{2}-{y}^{2}}\) orbital, for the same value of U and J used for the susceptibility. g, h focus on the low-temperature region, where Σ is plotted vs. T and T², respectively. The dashed line represents the best linear fit with the formula Σ = \(A({T}^{2}-{T}_{{{{{{{{\rm{FLFS}}}}}}}}}^{2})\), where A > 0. \({T}_{{{{{{{{\rm{CW}}}}}}}}}^{{\prime} }\), \({T}^{* {\prime} }\) and T_FLFS are the temperatures at which Σ flattens at high-temperature, the system starts to show a Fermi liquid behavior (linear dependence of Σ on T²), and Σ goes to zero at low-temperature respectively. Note that \({T}^{* {\prime} }\) ≈ T^*. The arrows show the position of various characteristic temperatures.