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 {\em first order Mott insulator to superconductor transition} in the CuO2 plane. We predict, i) {\em 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.
@article{arxiv.cond-mat/0505509,
title = {A resolution to doping asymmetry puzzle in high Tc cuprates},
author = {G. Baskaran},
journal= {arXiv preprint arXiv:cond-mat/0505509},
year = {2007}
}