Mott Insulator to HighTcSuperconductor via Pressure: Resonating Valence Bond Theory and Prediction of New Systems

Mott insulator superconductor transition, via pressure and no external doping, is studied in orbitally nondegenerate spin-$\frac{1}{2}$ systems. It is presented as another resonating valence bond route to high $T_c$ superconductivity. We propose a “strong coupling” hypothesis that views long range Coulomb force driven first order Mott transition as a self-doping process that also preserves superexchange on the metal side. We present a two-species $t\mathrm{\text{−}}J$ model where conserved $N_0$ doubly occupied ($e^{-}$) sites and $N_0$ empty sites ($e^{+}$) hop in the background of $N-2N_0$ singly occupied (neutral) sites in a lattice of $N$ sites. An equivalence to the regular $t\mathrm{\text{−}}J$ model is made. Some old and new systems are predicted to be candidates for pressure-induced high $T_c$ superconductivity.