Possible phase separation in the overdoped regime of La2−xSrxCuO4

Abstract

In order to investigate the possible inhomogeneous superconductivity in the overdoped high-Tc cuprates, suggested from the muon-spin-relaxation measurements, we have grown a single crystal of La2−xSrxCuO4 in which the Sr concentration, x, continuously changes in the overdoped regime and measured the magnetic susceptibility of several pieces of single crystals with different x values by slicing the single crystal. It has been found that the Meissner volume fraction, regarded as corresponding to the superconducting (SC) volume fraction in a sample, as well as Tc rapidly decreases with increasing x. It has been concluded that a phase separation into SC and normal-state regions takes place in a sample of La2−xSrxCuO4 in the overdoped regime. The separated two phases in the overdoped regime may be a hole-rich normal Fermi-liquid state region and a hole-poor superconducting one. Otherwise, holes doped into the Cu 3d orbital may destroy the superconductivity around themselves, producing normal-state regions in the superconducting sea.