Interlayer couplings in cuprates: mechanisms and structure-based estimators*

The cuprates superconductors are layered materials with one or more adjacent copper-oxygen (CuO₂) planes.  While the superconductivity is directly related to the in-plane electronic bands, the critical temperature varies with the number of adjacent CuO₂ planes [1], highlighting the importance of interlayer couplings.  However, multi-layer cuprates are more difficult to study due to the increased complexity of their unit cells.  Without a clear ab initio microscopic picture, interlayer couplings in cuprates are usually obtained empirically by tight-binding fits to the experimental photoemission spectra [2-3] which limits the understanding of microscopic mechanisms or engineering the materials.

Based on first-principles calculations, we identify multiple coexisting interlayer coupling mechanisms in cuprates and directly relate each to relevant structural properties.  We focus on the prototypical bilayer cuprates Bi₂Sr₂CaCu₂O_8+x (Bi-2212) and Pr_x+yY_1-xBa_2-yCu₃O₇ (Pr-YBCO) and demonstrate a method of estimating interlayer couplings, including their k-space dispersion, directly from the measured/computed crystal structure.  These mechanisms can hopefully lead to further design and engineering of these fascinating materials.

References

[1] Shimizu et al., J. Phys. Soc. Jpn. 78, 064705 (2009)

[2] Luo et al., Nat. Phys. https://doi.org/10.1038/s41567-023-02206-0 (2023)

[3] Kunisada et al., Science 369, 6505 (2020)