Inhomogeneous superconducting state in the overdoped regime of La 2−xSr xCuO 4: Comparison with the superconducting state of NbSe 2

Abstract

We have measured the temperature dependence of the magnetic susceptibility, χ vs. T, and the magnetization curve, M vs. H, for NbSe 2 single crystals, in order to compare the superconducting (SC) state in the overdoped regime of La 2− x Sr x CuO 4 (LSCO) with the SC state of the layered conventional superconductor NbSe 2. While a plateau in χ vs. T in a moderate magnetic field and a so-called second peak in M vs. H, which is due to the marked enhancement of vortex pinning, have been observed in the overdoped regime of LSCO, these behaviors have not been observed in NbSe 2. The present results indicate that the anomalously marked enhancement of vortex pinning is a characteristic feature in the overdoped LSCO where a microscopic phase separation into SC and normal-state regions takes place.