Finite-temperature phase diagram of nonmagnetic impurities in high-temperature superconductors using a d=3 tJ model with quenched disorder

We study a quenched disordered d=3 tJ Hamiltonian with static vacancies as a model of nonmagnetic impurities in high-T-c materials. Using a renormalization-group approach, we calculate the evolution of the finite-temperature phase diagram with impurity concentration p and find several features with close experimental parallels: Away from half filling, we see the rapid destruction of a spin-singlet phase (analogous to the superconducting phase in cuprates) which is eliminated for p greater than or similar to 0.05; in the same region for these dilute impurity concentrations, we observe an enhancement of anti ferromagnetism. The anti ferromagnetic phase near half filling is robust against impurity addition and disappears only for p greater than or similar to 0.40.