Impurity effects on dx2−y2-wave superconducting state in strongly correlated Hubbard model

Abstract

With cuprate superconductors in mind, we study the effects of point-type impurity potential (V) on a dx2−y2-wave superconducting (d-SC) state in a strongly correlated squarelattice Hubbard model (U/t = 12) with a diagonal transfer (t′), using a variational Monte Carlo method. At half filling, insulator-to-conductor (filling-control-type Mott) transitions occur at . The phase realized for is robust d-SC and the charge carriers are holes, whereas for a metallic (or weak d-SC) state appears with charge carriers of electrons. For a partially-filled case where the impurity density is equal to the doping rate, a d-SC-to-insulator transition arises at V ≡ VM ∼ 4t. In the weak-|V| phases, the impurity effects in the electron distribution are smeared out by the screening effect, whereas in the strong-|V| phases, the electron distribution directly depend on the impurity configurations.