Large-<i>n</i>limit of the Heisenberg-Hubbard model: Implications for high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>superconductors

The Heisenberg-Hubbard model is solved in the large-n limit to gain insight into its relevance to the coppper-oxide materials. A gapless disordered ground state is found for the Heisenberg model. Electronically induced orthorhombic-tetragonal symmetry breaking is observed as a function of doping, with the greatest tendency towards superconductivity occurring in the orthorhombic phase.