Spin texture ($\mathbf{s}(\mathbf{r})\text{ or }\mathbf{s}(\mathbf{k})$)

A spin texture describes how a spin expectation value or spin polarization varies with position or wavevector. It specifies a vector field, including its magnitude when that matters; a direction field alone is undefined wherever that magnitude vanishes. A Rashba spin texture is an example in which spin expectation values wind around circles in the plane of wavevectors.