DISAPPEARANCE OF SUPERCONDUCTIVITY IN OVERDOPED LA2-XSRXCUO4 AT A STRUCTURAL PHASE-BOUNDARY

The electronic and structural phase diagram of heavily doped La2-xSrxCuO4 (0.15 less-than-or-equal-to x less-than-or-equal-to 0.3) is reexamined. We demonstrate that the disappearance of superconductivity in "overdoped" La2-xSrxCuO4 is associated with an orthorhombic to tetragonal structural phase transition near x = 0.2, implying a relationship between superconductivity and subtle structural change. The bulk superconducting phase is thus confined to a much narrower composition range than believed. A complete solid solution of La and Sr is observed in the composition range investigated.