Structural anisotropy and chemical pressure effects on the superconducting transition in doped Bi-2201 cuprates

In this work, the relationship between crystal structure and the superconducting transition temperature Tc​ of the single-layer cuprate Bi2Sr2CuO6+δ (Bi-2201) was systematically analyzed using experimental data compiled from the literature. A total of 32 compositions, including La-, Pb-, and rare-earth–doped samples, were examined to clarify how chemical substitution affects the lattice parameters (a, b, c) and superconductivity. The analysis shows that chemical substitution induces anisotropic lattice distortion, characterized by a slight expansion of the in-plane parameters and a contraction of the c-axis, consistent with the effect of chemical pressure. A non-monotonic dependence of Tc​ on the structural parameters was identified, indicating that superconductivity is optimized within a specific range of lattice compression corresponding to intermediate values of the c/a ratio. These results demonstrate that interlayer geometry and lattice anisotropy play a key role in determining the superconducting properties of Bi-2201 and provide an experimental basis for evaluating theoretical models that link high-Tc superconductivity to structural dimensionality.