Electronic structure in the surface region: bulk and surface states

The electronic structure of Au(111) films is studied by means of relativistic DFT calculations. It is found that the twinning of the surface bands, observed in photoemission experiment, does not necessarily correspond to the spin-splitting of the surface states caused by the break of the inversion symmetry at the surface. The twinning of the bands of clean Au(111) films can be obtained within nonrelativistic or scalar-relativistic approximation, so that it is not a result of spin-orbit coupling. However, the spin-orbit coupling does not lead to the spin-splitting of the surface bands. This result is explained by Kramers’ degeneracy, which means that the existence of a surface itself does not destroy the inversion symmetry of the system. The inversion symmetry of the Au(111) film can be broken, for example, by means of adsorption, and a hydrogen monolayer deposited on one face of the film indeed leads to the appearance of the spin-splitting of the bands.

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Electronic structure in the surface region: electron-boson coupling in metallic systems

Physics of Solid Surfaces ◽

10.1007/978-3-662-53908-8_100 ◽

2018 ◽

pp. 416-420

Author(s):

P. D. Johnson

Keyword(s):

Electronic Structure ◽

Surface Region ◽

Boson Coupling ◽

Metallic Systems

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ELECTRONIC STRUCTURE AND RECONSTRUCTION OF THE Mo(001) SURFACE

Modern Physics Letters B ◽

10.1142/s0217984993000862 ◽

1993 ◽

Vol 07 (13n14) ◽

pp. 865-880 ◽

Cited By ~ 2

Author(s):

J.W. CHUNG ◽

K.S. SHIN ◽

S.C. HONG

Keyword(s):

Electronic Structure ◽

Charge Density Wave ◽

Density Wave ◽

Surface States ◽

Wave Model ◽

Theoretical Models ◽

Driving Mechanism ◽

Surface Electronic Structure ◽

Local Bonding ◽

Recent Developments

Recent developments in understanding the nature of surface electronic structure focused on illuminating the electronic origin of reconstruction of the Mo (001) surface have been reviewed. The long-standing disputes between two competing theoretical models, the charge density wave model and the local bonding model, for the driving mechanism of the reconstructional transition seem to be resolved by recent experimental evidences favoring the Peierls-type 2kF instabilities with significant matrix element effects. Details of recent experimental and theoretical findings for the surface electronic bands are discussed briefly with an emphasis placed on characterizing the surface states and their roles in the reconstruction.

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Andreev bound states in superconducting films and confined superfluid 3 He

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2015.0144 ◽

2018 ◽

Vol 376 (2125) ◽

pp. 20150144 ◽

Cited By ~ 3

Author(s):

Anton B. Vorontsov

Keyword(s):

Bound States ◽

Surface States ◽

Surface Region ◽

Theme Issue ◽

Confined Geometry ◽

Andreev Bound States ◽

Broken Symmetries ◽

Parent State ◽

Open Questions ◽

Coherence Lengths

This paper reviews confinement-driven phase transitions in superconductors and Bardeen–Cooper–Schrieffer superfluids, and the appearance in thin films of new phases that break the time-reversal or translational symmetry. The origins of the new phases are closely tied to the Andreev scattering processes involving particle-hole conversions that create surface quasiparticle states with energies inside the superconducting gap. Restructuring of the low-energy spectrum in the surface region of several coherence lengths ξ 0 results in large spatial variations of the superconducting order parameter. In confined geometry, such as slabs, films, pores or nano-dots, with one or more physical dimensions D ∼10 ξ 0 , the Andreev bound states can dominate properties of a superconductor, leading to modified experimental signatures. They can significantly change the energy landscape, and drive transitions into new superconducting phases. The new phases are expected in a variety of materials, from singlet d -wave superconductors to multi-component triplet superfluid 3 He, but properties of the new phases will depend on the symmetry of the parent state. I will highlight the connection between the Andreev surface states and confinement-stabilized phases with additional broken symmetries, describe recent progress and open questions in the theoretical and experimental investigation of superfluids in confined geometry. This article is part of the theme issue ‘Andreev bound states’.

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Crystallinity of tellurium capping and epitaxy of ferromagnetic topological insulator films on SrTiO3

Scientific Reports ◽

10.1038/srep11595 ◽

2015 ◽

Vol 5 (1) ◽

Cited By ~ 9

Author(s):

Jihwey Park ◽

Yeong-Ah Soh ◽

Gabriel Aeppli ◽

Xiao Feng ◽

Yunbo Ou ◽

...

Keyword(s):

Crystal Structure ◽

Electronic Structure ◽

Transport Properties ◽

Topological Insulator ◽

Topological Insulators ◽

Surface States ◽

Crystal Quality ◽

X Rays ◽

Capping Layer ◽

Subtle Effect

Abstract Thin films of topological insulators are often capped with an insulating layer since topological insulators are known to be fragile to degradation. However, capping can hinder the observation of novel transport properties of the surface states. To understand the influence of capping on the surface states, it is crucial to understand the crystal structure and the atomic arrangement at the interfaces. Here, we use x-ray diffraction to establish the crystal structure of magnetic topological insulator Cr-doped (Bi,Sb)2Te3 (CBST) films grown on SrTiO3 (1 1 1) substrates with and without a Te capping layer. We find that both the film and capping layer are single crystal and that the crystal quality of the film is independent of the presence of the capping layer, but that x-rays cause sublimation of the CBST film, which is prevented by the capping layer. Our findings show that the different transport properties of capped films cannot be attributed to a lower crystal quality but to a more subtle effect such as a different electronic structure at the interface with the capping layer. Our results on the crystal structure and atomic arrangements of the topological heterostructure will enable modelling the electronic structure and design of topological heterostructures.

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