LAUSR

First-principles electronic structure calculations have been employed to identify the nature of spin textures induced by Rashba-Dresselhaus effect in the ferroelectric systems ${\mathrm{LaWN}}_{3}$ (LWN), ${\mathrm{Ag}}_{2}{\mathrm{BiO}}_{3}$ (ABO), and ${\mathrm{BiInO}}_{3}$ (BIO). Calculations reveal Rashba spin texture in LWN, Dresselhaus spin texture in ABO and unidirectional persistent spin helix (PSH) in BIO hosted by the conduction bands around the high-symmetry $Z$ point of the Brilliouin zone (BZ) despite all these systems belonging to the same point group symmetry ${\mathrm{C}}_{2v}$. We propose that in addition to the local symmetry, the orbital character of the bands at the high-symmetry point of the BZ play a crucial role in determining the spin textures. A systematic study indeed reveals that the orbital characters of the conduction bands at the $Z$ point for these three systems are markedly different, where in the presence of SOC it is predominantly W-$d$ character in LWN, Bi-$s+\mathrm{O}\text{\ensuremath{-}}{p}_{z}$ character in ABO and Bi-${p}_{x}$ character in BIO, suggesting the important role of orbital degrees of freedom in tailoring spin texture. Further we explain, while nonsymmorphic symmetry hosts out of plane spin component in the spin texture for LWN and BIO, enhancing the band splitting at the ${\mathrm{k}}_{z}=\ensuremath{\pi}/c$ plane, this is however not present in ABO. Our first-principles results are supplemented with an effective $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ model confirming the important role of orbital symmetry.