Beyond Rashba: Persistent spin textures as a design principle for spin-orbitronics

Crystal symmetries significantly impact the behavior of electrons in solids, including how their spins align and evolve. A particularly important consequence is spin-momentum locking, which defines how an electron’s spin orientation is tied to its momentum. Spin-momentum locking plays a central role in determining the geometry and efficiency of charge-to-spin conversion as well as the spin relaxation. These properties are essential for spin-orbitronic devices.

In this talk, I will focus on a special form of spin-momentum locking known as persistent spin texture (PST), where the spin orientation remains unidirectional and independent of momentum over extended regions of the Brillouin zone. Contrary to earlier assumptions that PST is rare, we show that it is a universal feature of all nonmagnetic crystals without inversion symmetry. While the general conditions for PST stem from symmetry principles, I will focus on its physical manifestations and implications for spin transport.

A particularly interesting case arises in chiral crystals, where PST evolves from an anisotropic radial spin texture. This configuration enhances both charge-to-spin conversion efficiency and spin lifetimes. I will illustrate this behavior using chiral tellurium as a case study, combining theoretical analysis with first-principles simulations to highlight its potential as a high-performance spin transport material. To conclude, I will outline general strategies for designing PST materials and illustrate them with a few representative examples.