Persistent spin textures in nonpolar chiral systems

We propose a route for the realization of persistent spin texture (PST). We have shown from symmetry considerations that in nonpolar chiral systems, bands with specific orbital characters around a high-symmetry point with ${D}_{2}$ little group may admit a single spin-dependent term in the low-energy $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ model Hamiltonian that naturally leads to PST. Considering a two-dimensional plane in the Brillouin zone, we have further argued that in such chiral systems, the PST is transpired due to the comparable strengths of the Dresselhaus and Weyl (radial) interaction parameters where the presence of these two terms is allowed by the $D{}_{2}$ symmetry. Finally, using first-principles density functional theory calculations, we have identified that the nonpolar chiral compounds ${\mathrm{Y}}_{3}{\mathrm{TaO}}_{7}$ and ${\mathrm{AsBr}}_{3}$ displays PST for the conduction band and valence band, respectively, around the $\mathrm{\ensuremath{\Gamma}}$ point having $D{}_{2}$ little group and predominantly Ta-${d}_{xz}$ orbital character for ${\mathrm{Y}}_{3}{\mathrm{TaO}}_{7}$ and Br-$p{}_{x}$ orbital character for ${\mathrm{AsBr}}_{3}$, corroborating our general strategy. Our results for the realization of PST in nonpolar chiral systems thereby broaden the class of materials displaying PST that can be employed for application in spin orbitronics.