DISORDER AND QUANTUM CRITICALITY IN d-WAVE SUPERCONDUCTORS.

To explain experimentally observed quasiparticle relaxation rates in the cuprate superconductors, Sachdev and collaborators recently proposed that the d-wave system may be close to a quantum critical point towards a superconducting state with an additional order parameter component of is- or id-wave symmetry. In the proximity of the transition, dynamical order parameter fluctuations modify the system properties. Here, we explore the influence of disorder on this interacting fluctuation regime. Our main finding is that unlike in the clean system, significant qualitative differences between is and id exist: In the is-case, due to the disorder-enhanced low-energy density of states, a secondary superconducting transition (with a strongly disorder-dependent Tc) takes place. In contrast, in the id-case essential features of the clean scenario are left intact by the disorder. [ABSTRACT FROM AUTHOR]