Enhanced superconducting T-c in the immiscible system (La1.85Sr0.15CuO4)(x)(Lu2Cu2O5)(1-x)

Abstract

We discovered that the immiscibility between La1.85Sr0.15CuO4 and Lu2Cu2O5 leads to a micrometer-scale heterogeneous mixture of a superconducting cuprate and an antiferromagnetic insulator. Whereas electronic conduction of the mixture in the normal state exhibits a percolation behavior, superconducting T-c systematically increases with increasing amounts of insulating Lu2Cu2O5. The highest onset T-c of 46 K is achieved near the percolation threshold. Even though an unusual magnetic proximity effect cannot be ruled out, a plausible cause for the Tc enhancement is the tensile strain in highly anisotropic La1.85Sr0.15CuO4 induced by the differential thermal contraction of the two phases.