Effect of rare-gas adsorption on the spin-orbit split bands of a surface alloy: Xe on Ag(111)-(root 3 x root 3) R30 degrees-Bi

We have investigated by angle-resolved photoemission spectroscopy changes induced by Xe adsorption on the spin-orbit-split bands of the epitaxial Ag(111) (root 3x root 3)R30 degrees-Bi surface alloy. We observe an extensive backfolding of the alloy band structure due to the formation of a 9 x 9 commensurate or quasicommensurate Xe overlayer and the opening of a small hybridization gap at the intersection of two sets of bands of (primarily) Bi sp(z) and p(xy) characters. The large spin-orbit splitting of the substrate bands is essentially unaffected by the Xe overlayer, in sharp contrast to the enhancement reported for the clean Au(111) surface. This points to different mechanisms at the origin of the splitting in the clean surfaces and in the surface alloy.

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Christian Reinhard Ast, Marco Grioni, Luca Moreschini
2008
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https://infoscience.epfl.ch/record/148041?ln=fr

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Electronic structure of an ordered Pb/Ag(111) surface alloy: Theory and experiment

Christian Reinhard Ast, Marco Grioni, Luca Moreschini, Daniela Pacilè

We have studied by angle-resolved photoelectron spectroscopy (ARPES) the band structure of the ordered surface alloy obtained by the deposition of 0.33 monolayers of Pb on the Ag(111) surface. We observe several dispersing features which are well described as Pb-Ag hybrid bands by a band structure calculation performed within the generalized gradient approximation of density functional theory. We also find that a band of mixed Pb p(z) and Ag s character is split in momentum space. We interpret this splitting as the combined result of spin-orbit interaction and broken inversion symmetry at the surface.

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Origin of Rashba splitting in the quantized subbands at the Bi2Se3 surface

Christian Reinhard Ast, Klaus Kern

We study the band structure of the Bi2Se3 topological insulator (1 1 1) surface using angle-resolved photoemission spectroscopy. We examine the situation where two sets of quantized subbands exhibiting different Rashba spin splitting are created via bending of the conduction (CB) and the valence (VB) bands at the surface. While the CB subbands are strongly Rashba spin split, the VB subbands do not exhibit clear spin splitting. We find that CB and VB experience similar band bending magnitudes, which means, a spin-splitting discrepancy due to different surface potential gradients can be excluded. On the other hand, by comparing the experimental band structure to first-principles LMTO band structure calculations, we find that the strongly spin-orbit coupled Bi 6p orbitals dominate the orbital character of CB, whereas their admixture to VB is rather small. The spin-splitting discrepancy is, therefore, traced back to the difference in spin-orbit coupling between CB and VB in the respective subbands' regions.

Amer Physical Soc2013

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Surface and bulk electronic structure of the strongly correlated system SmB6 and implications for a topological Kondo insulator

Kazimierz Conder, Jan Hugo Dil, Joël Mesot

Recent theoretical calculations and experimental results suggest that the strongly correlated material SmB6 may be a realization of a topological Kondo insulator. We have performed an angle-resolved photoemission spectroscopy study on SmB6 in order to elucidate elements of the electronic structure relevant to the possible occurrence of a topological Kondo insulator state. The obtained electronic structure in the whole three-dimensional momentum space reveals one electron-like 5d bulk band centered at the X point of the bulk Brillouin zone that is hybridized with strongly correlated f electrons, as well as the opening of a Kondo band gap (Delta(B) similar to 20 meV) at low temperature. In addition, we observe electron-like bands forming three Fermi surfaces at the center Gamma point and boundary (X) over bar point of the surface Brillouin zone. These bands are not expected from calculations of the bulk electronic structure, and their observed dispersion characteristics are consistent with surface states. Our results suggest that the unusual low-temperature transport behavior of SmB6 is likely to be related to the pronounced surface states sitting inside the band hybridization gap and/or the presence of a topological Kondo insulating state.

Amer Physical Soc2013

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