The optical transitions between spin-polarized bands of the quasi-two dimensional Rashba system BiTeI are investigated using polarization resolved resonant Raman spectroscopy. We detect chiral excitations between states with opposite helicity and compare spectra to calculations within a three- band model. Using the resonant Raman excitation profile, we deduce the Rashba parameters and band gaps of the higher conduction bands near the Fermi level, and compare the parameters to values obtained by ab initio density function theory (DFT).
By comparing spectroscopic data to calculations within a three-band model, the CB1 band was confirmed to have a Rashba dispersion with parameters similar to those given by DFT: ∆1 = 1.48 eV, αR = 1.35 eV ̊A and m∗ = 0.15 me. The CB2 parabolic dispersion differs significantly from DFT calculations: (∆2 , m∗ ) = (1.65 eV, 0.14 me ) vs. (2.05 eV, 0.34 me ) as calculated by DFT. Under resonance, the CB2→CB0 transition ap- pear partially polarized, suggesting that CB2 is also spin- polarized away from the A-point.
More generally, the presented approach of studying BiTeI may enable control of chiral electronic excitations in systems with a strong Rashba-like dispersion and offer critical insight into novel chirality-based phenomena in quasi-2D Rashba systems.
ArXiv Link: arXiv:2202.03569 PDF: File