A resolution to doping asymmetry puzzle in high Tc cuprates

Abstract

We present a microscopic model for `electron doped' $N{d}_{2-x}C{e}_{x}Cu{O}_4$ 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 $C{u}^{2+}$ spin moment at an adjacent site, at an energy scale > superexchange J of $Cu{O}_2$ 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 $Cu{O}_2$ 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.

4 pages LaTex file, 4 figures eps files, typos corrected