Superconducting/non-superconducting phase boundary in the low temperature tetragonal phase of (La,RE)-Sr-Cu-O

From measurements of the structural, superconducting and normal state transport properties of rare earth doped La{sub 2{minus}x}Sr{sub x}CuO{sub 4} the authors find a phase boundary between a superconducting and a non-superconducting state of the low temperature tetragonal phase. This phase boundary is determined by the magnitude of the buckling of the Cu-O-Cu bonds in the CuO{sub 2} layers, suggesting the importance of spin-orbit coupling for the electronic properties of these compounds.