Inhomogeneous superconducting state in the overdoped regime of La2-xSrxCuO4: Comparison with the superconducting state of NbSe2

We have measured the temperature dependence of the magnetic susceptibility, chi vs. T, and the magnetization curve, M vs. H, for NbSe2 single crystals, in order to compare the superconducting (SC) state in the overdoped regime of La2-xSrxCuO4 (LSCO) with the SC state of the layered conventional superconductor NbSe2. While a plateau in chi 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 overcloped regime of LSCO, these behaviors have not been observed in NbSe2. The present results indicate that the anomalously marked enhancement of vortex pinning is a characteristic feature in the overcloped LSCO where a microscopic phase separation into SC and normal-state regions takes place. (C) 2008 Elsevier Ltd. All rights reserved.