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تسجيل مستخدم جديدThe critical nature of the Ni spin state in doped NdNiO$_2$
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Superconductivity with $T_c approx 15K$ was recently found in doped NdNiO$_2$. The Ni$^{1+}$O$_2$ layers are expected to be Mott insulators so hole doping should produce Ni$^{2+}$ with $S=1$, incompatible with robust superconductivity. We show that the NiO$_2$ layers fall inside a ``critical region where the large $pd$ hybridization favors a singlet $^1!A_1$ hole-doped state like in CuO$_2$. However, we find that the superexchange is about one order smaller than in cuprates, thus a magnon ``glue is very unlikely and another mechanism needs to be found.
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