A resolution to doping asymmetry puzzle in high Tc cuprates

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We present a microscopic model for `electron doped' Nd₂₋ₓCeₓCuO₄ family and offer a resolution to a long standing doping asymmetry puzzle. Here, i) Ce atoms do not dope free electrons, instead a Ce atom effectively quenches a Cu²⁺ spin moment at an adjacent site, at an energy scale > superexchange J of CuO₂ plane and `site dilutes' the Mott insulator. ii) Effective chemical pressure, caused by increased Ce substitution, induces a first order Mott insulator to superconductor transition in the CuO₂ plane. We predict, i) equal number of +e and -e carriers in metallic state and ii) a line of first order transition ending at a critical point in normal state. Phenomenology gets organized.