TL;DR: The observation of a giant spin-orbit splitting of quantum-well states in the unoccupied electronic structure of a Bi monolayer on Cu(111) allows for the direct possibility to tailor spin- orbit splitting by means of thin-film nanofabrication.
Abstract: We report on the observation of a giant spin-orbit splitting of quantum-well states in the unoccupied electronic structure of a Bi monolayer on Cu(111). Up to now, Rashba-type splittings of this size have been reported exclusively for surface states in a partial band gap. With these quantum-well states we have experimentally identified a second class of states that show a huge spin-orbit splitting. First-principles electronic structure calculations show that the origin of the spin-orbit splitting is due to the perpendicular potential at the surface and interface of the ultrathin Bi film. This finding allows for the direct possibility to tailor spin-orbit splitting by means of thin-film nanofabrication.
TL;DR: The finding of a huge spin-orbit interaction effect in a polar semiconductor composed of heavy elements, BiTeI, where the bulk carriers are ruled by large Rashba-likespin splitting is described, confirming that the spin splitting is indeed derived from bulk atomic configurations.
Abstract: A very large Rashba-type spin splitting, which is a consequence of spin–orbit interaction, has been observed in the heavy-element semiconductor BiTeI. The results show the possibility, in principle, of using the material in spintronics devices in which the electron spin is controlled by electric currents.
TL;DR: A theoretical investigation of Rashba band splitting in ferroelectric halide perovskite materials indicates that and Rashba bands directly coupled to ferro electric polarization emerge at the valence and conduction band edges, respectively.
Abstract: The Rashba effect is spin degeneracy lift originated from spin-orbit coupling under inversion symmetry breaking and has been intensively studied for spintronics applications. However, easily implementable methods and corresponding materials for directional controls of Rashba splitting are still lacking. Here, we propose organic-inorganic hybrid metal halide perovskites as 3D Rashba systems driven by bulk ferroelectricity. In these materials, it is shown that the helical direction of the angular momentum texture in the Rashba band can be controlled by external electric fields via ferroelectric switching. Our tight-binding analysis and first-principles calculations indicate that S = 1/2 and J = 1/2 Rashba bands directly coupled to ferroelectric polarization emerge at the valence and conduction band edges, respectively. The coexistence of two contrasting Rashba bands having different compositions of the spin and orbital angular momentum is a distinctive feature of these materials. With recent experimental evidence for the ferroelectric response, the halide perovskites will be, to our knowledge, the first practical realization of the ferroelectric-coupled Rashba effect, suggesting novel applications to spintronic devices.
Cites background from "Quantum-well-induced giant spin-orb..."
...To date, major concerns have focused on enlarging Rashba strength characterized by the Rashba coefficient αR (3, 5, 6)....
TL;DR: It is demonstrated, using density function theory calculations and experiments, that it is possible to create helical Dirac fermion state by interfacing two gapped films-a single bilayer Bi grown on a single quintuple layer Bi( 2)Se(3) or Bi(2)Te(3).
Abstract: Topological insulators are a unique class of materials characterized by a Dirac cone state of helical Dirac fermions in the middle of a bulk gap. When the thickness of a three-dimensional topological insulator is reduced, however, the interaction between opposing surface states opens a gap that removes the helical Dirac cone, converting the material back to a normal system of ordinary fermions. Here we demonstrate, using density function theory calculations and experiments, that it is possible to create helical Dirac fermion state by interfacing two gapped films-a single bilayer Bi grown on a single quintuple layer Bi(2)Se(3) or Bi(2)Te(3). These extrinsic helical Dirac fermions emerge in predominantly Bi bilayer states, which are created by a giant Rashba effect with a coupling constant of ~4 eV·A due to interfacial charge transfer. Our results suggest that this approach is a promising means to engineer topological insulator states on non-metallic surfaces.
TL;DR: It is predicted that stable BiTeX (X = Br and I) monolayers possess intrinsic large polar electric fields along the normal direction to the plane, making them two-dimensional polar systems and promising for wide applications in nanoelectronics.
Abstract: A number of graphene-like materials have been theoretically predicted and experimentally confirmed so far. Here, based on the first-principles calculations, we predict that stable BiTeX (X = Br and I) monolayers possess intrinsic large polar electric fields along the normal direction to the plane, making them two-dimensional polar systems. Moreover, we find that these novel monolayers with thicknesses of only 3.8 A can produce a giant Rashba spin splitting derived from their peculiarly polar atomic configurations. Furthermore, the Rashba parameters of BiTeX monolayers can be effectively modulated by applying strain, and are thus promising for wide applications in nanoelectronics.
TL;DR: In this article, the bulk band structure and surface states of BiTeBr were studied within density functional theory and both ordered and disordered phases, which differ in atomic order in the Te-Br sublattice.
Abstract: Within density functional theory, we study the bulk band structure and surface states of BiTeBr. We consider both ordered and disordered phases, which differ in atomic order in the Te–Br sublattice. On the basis of relativistic ab initio calculations, we show that the ordered BiTeBr is energetically preferable as compared with the disordered one. We demonstrate that both Te- and Br-terminated surfaces of the ordered BiTeBr hold surface states with a giant spin–orbit splitting. The Te-terminated surface-state spin splitting has Rashba-type behavior with the coupling parameter αR ~ 2 eVA.