Tuning the Ground State of Cuprate Superconducting Thin Films by Nanofaceted Substrates

Anisotropic transport properties have been assessed in a number of cuprate superconductors, providing evidence for a nematic state. Here, we analyze recent experimental data for ultrathin YBa_2Cu_3O_7-x (YBCO) films, where nematicity is induced via strain engineering, leading to a suppression of charge density wave scattering along the orthorhombic a-axis and a concomitant enhancement of strange metal behavior along the b-axis. It is shown that the anisotropic properties strongly depend on the substrate, which we characterize by atomic force microscopy (AFM). Based on the AFM data, we provide a microscopic model that can account for the absence (presence) of nematicity and the resulting transport properties in films grown on SrTiO_3 (MgO) substrates.