Persistence of the topological surface states in Bi2Se3 against Ag intercalation at room temperature

The electronic and atomic structures of topological insulator Bi2Se3, upon Ag atom deposition, have been investigated by combined experimental methods of scanning tunneling microscopy (STM), photoelectron spectroscopy, and first-principles calculations. We show from the results of STM that the deposited Ag atoms are stabilized beneath the surface instead of being adsorbed on the topmost surface. We further reveal from the angle-resolved photoemission spectroscopy that the Bi2Se3(0001) topological surface states stay uninterrupted after a large amount of absorption of Ag atoms. Our analysis of the photoelectron intensity of Ag core states excited by soft X-ray suggests that a large amount of deposited Ag atoms diffused into a deeper place, which is beyond the probing depth of X-ray photoelectron spectroscopy. The first-principles calculations identify the octahedral site in the van der Waals gaps between quintuple layers to be the most favorable locations of Ag atoms beneath the surface, which yields good agreement between the simulated and experimental STM images. These findings pave an efficient way to tailor the local lattice structures of topological insulators without disturbing the topologically nontrivial surface states

Quasiparticle interference on the surface of Bi2Se3 induced by cobalt adatom in the absence of ferromagnetic ordering

Quasiparticle interference induced by cobalt adatoms on the surface of the topological insulator Bi2Se3 is studied by scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and x-ray magnetic circular dichroism. It is found that Co atoms are selectively adsorbed on top of Se sites and act as strong scatterers at the surface, generating anisotropic standing waves. A long-range magnetic order is found to be absent, and the surface state Dirac cone remains gapless. The anisotropy of the standing wave is ascribed to the heavily warped iso-energy contour of unoccupied states, where the scattering is allowed due to a nonzero out-of-plane spin

Unified description of the electronic structure of M 2 A C nanolamellar carbides

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Photoemission study of the IBr graphite intercalation compound using the synchrotron radiation light source

We measured the photoemission spectra of the IBr graphite intercalation compounds (IBr-GIC) with stage-2 and stage-4 structures at 16 K with incident photon energies hν=40-200 eV. The peak positions of the I 4d and Br 3d core-levels are unchanged for the stage-2 and stage-4 IBr-GICs. Partial density-of-states of the I 5p and Br 4p states in the valence bands have been evaluated by resonant photoemission spectroscopy. These spectra indicate a significant hybridization between the host and the guest IBr in the van der Waals gap

Epitaxial growth of honeycomb-like stanene on Au(111)

International audienceStanene, which is predicted to be a quantum spin Hall topological insulator with tunable topological state, seems to be the most promising candidate of the post-graphene elemental two-dimensional (2D) materials. Here, we prepared epitaxial honeycomb-like stanene on gold (111) substrates and investigated its superstructure by Low Energy Electron Diffraction and Scanning Tunneling Microscopy. Angle-Resolved PhotoEmission Spectroscopy was applied to explore the electronic structures, further confirmed by first principles calculations. The stanene-like sheet forms a nearly planar structure on the Au(111) surface with a "2×√3" superstructure in large surface areas. Core-level spectroscopy reveals that the stanene-like sheet lays almost directly on the Au(111) surface. This is consistent with DFT calculations of the atomic structure. A characteristic 2D band with parabolic dispersion is observed