Strong correlations make high-temperature superconductors robust against disorder

Abstract

Why are the superconducting pairs in high-temperature superconductors so resilient to the presence of disorder? The strong electronic correlations appear to be the answer. Strong correlations are central to the problem of high-temperature superconductivity in the cuprates1,2,3,4. Correlations are responsible for both the Mott insulating, antiferromagnetic state in the parent compounds and for the d-wave superconducting state that arises on doping with mobile charge carriers. An important experimental fact about the superconducting state is its insensitivity to disorder5, in marked contrast with conventional theories of d-wave pairing, which predict just the opposite. Here, we generalize the theory of the strongly correlated superconducting ground state based on projected wavefunctions6,7,8,9 to include impurity effects and find the remarkable result that correlations play a central role in making the superconductor robust against disorder. The nodal quasiparticles, which are the low-energy electronic excitations, are protected against disorder leading to characteristic signatures in scanning tunnelling spectroscopy10,11,12,13,14 and angle-resolved photoemission15,16,17.