Visualization of the spin-resolved band structure in the bulk Rashba material BiTeCl

The spin-orbit interaction has been studied intently, as it provides a mechanism for topologically non-trivial phenomena. Noncentrosymmetric materials with strong spin-orbit interactions can give rise to the bulk Rashba effect, such as the material family BiTeX (X=Cl, Br, I). Angle-resolved photoemission spectroscopy (ARPES) has shown that BiTeX possesses spin-split bands with some of the largest measured values of the Rashba parameter. Beyond conventional ARPES, spin-resolved ARPES is a powerful tool to directly probe their rich spin-orbital textures. In this talk, we will present our recent spin-resolved ARPES work on BiTeCl in which we visualize the detailed Rashba-split bands and quantitatively track the spin texture. We show that the momentum-dependent spin polarization cannot be fully described by the usual Rashba Hamiltonian. Thus, we apply a third-order Rashba model constrained by the crystal point group symmetry, which shows remarkable agreement with the measured spin structure. Furthermore, we use ab initio calculations to support our interpretations and give insights into the possible microscopic mechanisms that lead to such spin-orbital interactions.