摘要
Spin-split Rashba bands have been exploited to efficiently control the spin degree of freedom of moving electrons, which possesses a great potential in frontier applications of designing spintronic devices and processing spin-based information. Given that intrinsic breaking of inversion symmetry and sizeable spin-orbit interaction, two-dimensional (2D) surface alloys formed by heavy metal elements exhibit a pronounced Rashba-type spin splitting of the surface states. Here, we have revealed the essential role of atomic orbital symmetry in the hexagonally warped Rashba spin-split surface state of√3̅×√3̅ R30°BiCu ₂monatomic alloy by scanning tunneling spectroscopy (STS) and density functional theory (DFT). From\mathrm{d}{I}{/}\mathrm{d}{U}{}spectra and calculated band structures, three hole-like Rashba-split bands hybridized from distinct orbital symmetries have been identified in the unoccupied energy region. Because of the hexagonally deformed Fermi surface, quasi-particle interference (QPI) mappings have resolved scattering channels opened from interband transitions of p ₓ, p _(y) ( mⱼ=1/2 ) band. In contrast to the s,p _(z) -derived band, the hexagonal warping predominately is accompanied by substantial out-of-plane spin polarizationS_(z)up to 24% in the dispersion of p ₓ ,p _(y) ( mⱼ=1/2 ) band with an in-plane orbital symmetry.