Uncovering and tailoring hidden Rashba spin-orbit splitting in centrosymmetric crystals

TL;DR

This paper reveals the microscopic mechanisms behind hidden Rashba spin-splitting in centrosymmetric crystals, showing how local symmetries enforce spin segregation and how external fields can tailor these effects.

Contribution

It uncovers the symmetry-based origin of R-2 spin-splitting and demonstrates how effective Hamiltonians apply to both R-1 and R-2 effects, enabling targeted spin control.

Findings

Spin-splitting in R-2 is enforced by specific symmetries.

Local sector symmetries are fundamental to Rashba effects.

External electric fields can modify spin-splitting patterns.

Abstract

Hidden Rashba and Dresselhaus spin-splittings in centrosymmetric crystals with subunits (sectors) having non-centrosymmetric symmetries (the R-2 and D-2 effects) have been predicted and observed experimentally, but the microscopic mechanism remains unclear. Here we demonstrate that the spin-splitting in R-2 is enforced by specific symmetries (such as the non-symmorphic in the present example) which ensures that the pertinent spin wavefunctions segregate spatially on just one of the two inversion-partner sectors and thus avoid compensation. This finding establishes a common fundamental source for the conventional Rashba (R-1) effect and the R-2 effect, both originating from the local sector symmetries, rather than from the global crystal asymmetry alone for R-1 per se. We further show that the effective Hamiltonian for the R-1 effect is also applicable for the R-2 effect, but applying a symmetry-breaking electric field to an R-2 compound produces different spin-splitting pattern than applying a field to a trivial (non-R-2) centrosymmetric compound.