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Register a new userSpin-polarized surface states close to adatoms on Cu(111)
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We present a theoretical study of surface states close to 3d transition metal adatoms (Cr, Mn, Fe, Co, Ni and Cu) on a Cu(111) surface in terms of an embedding technique using the fully relativistic Korringa-Kohn-Rostoker method. For each of the adatoms we found resonances in the s-like states to be attributed to a localization of the surface states in the presence of an impurity. We studied the change of the s-like densities of states in the vicinity of the surface state band-edge due to scattering effects mediated via the adatoms d-orbitals. The obtained results show that a magnetic impurity causes spin-polarization of the surface states. In particular, the long-range oscillations of the spin-polarized s-like density of states around an Fe adatom are demonstrated.
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The characterization and applications of topological insulators depend critically on their protected surface states, which, however, can be obscured by the presence of trivial dangling bond states. Our first principle calculations show that this is the case for the pristine $(111)$ surface of SnTe. Yet, the predicted surface states unfold when the dangling bond states are passivated in proper chemisorption. We further extract the anisotropic Fermi velocities, penetration lengths and anisotropic spin textures of the unfolded $barGamma$- and $bar M$-surface states, which are consistent with the theory in http://dx.doi.org/10.1103/PhysRevB.86.081303 Phys. Rev. B 86, 081303 (R). More importantly, this chemisorption scheme provides an external control of the relative energies of different Dirac nodes, which is particularly desirable in multi-valley transport.
Low-temperature scanning tunneling spectroscopy reveals that the Kondo temperature T_K of Co atoms adsorbed on Cu/Co/Cu(100) multilayers varies between 60 K and 134 K as the Cu film thickness decreases from 20 to 5 atomic layers. The observed change of T_K is attributed to a variation of the density of states at the Fermi level rho_F induced by quantum well states confined to the Cu film. A model calculation based on the quantum oscillations of rho_F at the belly and the neck of the Cu Fermi surface reproduces most of the features in the measured variation of T_K.
We present angle-resolved photoemission data from Cu(111). Using a focused 6 eV continuous wave laser for photo-excitation, we achieve a high effective momentum resolution enabling the first detection of the Rashba spin splitting in the Shockley surface state on Cu(111). The magnitude of the spin-splitting of Delta k ~ 0.006 A^-1 is surprisingly large and exceeds values predicted for the analogous surface state on Ag(111) but is reproduced by first principles calculations. We further resolve a kink in the dispersion which we attribute to electron-phonon coupling.
The topological order of single-crystal Bi and its surface states on the (111) surface are studied in detail based on empirical tight-binding (TB) calculations. New TB parameters are presented that are used to calculate the surface states of semi-infinite single-crystal Bi(111), which agree with the experimental angle-resolved photoelectron spectroscopy results. The influence of the crystal lattice distortion is surveyed and a topological phase transition is found that is driven by in-plane expansion. In contrast with the semi-infinite system, the surface-state dispersions on finite-thickness slabs are non-trivial irrespective of the bulk topological order. The role of the interaction between the top and bottom surfaces in the slab is systematically studied, and it is revealed that a very thick slab is required to properly obtain the bulk topological order of Bi from the (111) surface state: above 150 biatomic layers in this case.
We present a study of graphene/substrate interactions on UHV-grown graphene islands with minimal surface contamination using emph{in situ} low-temperature scanning tunneling microscopy (STM). We compare the physical and electronic structure of the sample surface with atomic spatial resolution on graphene islands versus regions of bare Cu(111) substrate. We find that the Rydberg-like series of image potential states is shifted toward lower energy over the graphene islands relative to Cu(111), indicating a decrease in the local work function, and the resonances have a much smaller linewidth, indicating reduced coupling to the bulk. In addition, we show the dispersion of the occupied Cu(111) Shockley surface state is influenced by the graphene layer, and both the band edge and effective mass are shifted relative to bare Cu(111).
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