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 T c ​ of the single-layer cuprate Bi 2 Sr 2 CuO 6 + 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 T c ​ 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- T c superconductivity to structural dimensionality.

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