Coupling between superconductivity and structural deformation in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$ (x∼0.13)

Capacitance-dilatometer measurements of the anisotropic thermal expansion on a superconducting single crystal of ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ (x∼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 ${\mathit{T}}_{\mathit{c}}$ the tilt of the ${\mathrm{CuO}}_6$ octahedra related to the structural phase transition is frozen in.