COUPLING BETWEEN SUPERCONDUCTIVITY AND STRUCTURAL DEFORMATION IN LA2-XSRXCUO4 (X-SIMILAR-TO-0.13)

Capacitance-dilatometer measurements of the anisotropic thermal expansion on a superconducting single crystal of La2-xSrxCuO4 (x approximately 0.13) show large anomalies at the structural transition from the high-temperature tetragonal to the low-temperature orthorhombic phase followed by smaller anomalies of the opposite sign at the superconducting phase transition. Neutron-diffraction experiments on the same crystal indicate that at T(c) the tilt of the CuO6 octahedra related to the structural phase transition is frozen in.