Each unit cell in YBa2Cu3O6+x contains a pair of two-dimensional CuO2 layers. While the crystal structure is globally inversion symmetric, the individual layers are not. This leads, necessarily, to a nonvanishing Rashba spin-orbit coupling (SOC) in the CuO2 layers, with opposite signs of the coupling constant in each layer. These so-called Rashba bilayers generate hidden spin textures, with a vansishing net spin at each k-point in the Brillouin zone, but nonvanishing spin textures in each layer separately. Here, we trace the microscopic origin of the Rashba splitting through the orbital structure of the CuO2 conduction bands, obtain a generic three-orbital model Hamiltonian, and show that the magnitude of the spin-splitting predicted by density functional theory is ∼10~meV.
@article{arxiv.1910.11444,
title = {Microscopic model for the hidden Rashba effect in YBa$_2$Cu$_3$O$_{6+x}$},
author = {W. A. Atkinson},
journal= {arXiv preprint arXiv:1910.11444},
year = {2020}
}