Dopant-induced stabilization of three-dimensional charge order in the cuprate YBCO7

We investigate the microscopic mechanisms behind the stabilization of three-dimensional (3D) charge order by Pr doping in YBa₂Cu₃O₇ (YBCO7): experimentally, this material shows a spectacularly well-defined static 3D charge order peak [1].  Our density-functional-theory calculations describe the structure of the lowest-energy Pr superlattices for both Ba- and Y-site substitutions. In the Ba-site case, the smaller Pr ion pulls the surrounding atoms inward. This breathing-mode distortion pins charge-stripe walls to the Pr columns and forces them to align along the c axis. However, Y-site substituted Pr is larger than the host Y ion, produces an outward distortion, and fails to pin the stripes. Our coarse-grained Monte-Carlo simulations show that the stripe correlation length directly follows the structural correlation length of the Pr dopant as observed in prior experiments. We thus propose dopant-induced lattice pinning as the key mechanism behind static 3D charge order in Pr-doped YBCO7. This approach provides quantitative guidelines for engineering electronic orders through targeted ionic substitution.

[1] Ruiz et al., Nature Communications vol. 13,  article no. 6197 (2022)  DOI https://doi.org/10.1038/s41467-022-33607-z