scholarly journals Topological surface states and Andreev bound states in superconducting iron pnictides

2014 ◽  
Vol 90 (2) ◽  
Author(s):  
Alexander Lau ◽  
Carsten Timm
Keyword(s):  
Bound States ◽  
Surface States ◽  
Iron Pnictides ◽  
Andreev Bound States ◽  
Topological Surface

scholarly journals Andreev bound states in superconducting films and confined superfluid 3 He

2018 ◽  
Vol 376 (2125) ◽  
pp. 20150144 ◽  
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’.

scholarly journals Reappearance of first Shapiro step in narrow topological Josephson junctions

2021 ◽  
Vol 7 (26) ◽  
pp. eabf1854
Author(s):  
Daniel Rosenbach ◽  
Tobias W. Schmitt ◽  
Peter Schüffelgen ◽  
Martin P. Stehno ◽  
Chuan Li ◽  
...  
Keyword(s):  
Josephson Junctions ◽  
Bound States ◽  
Weak Link ◽  
Surface States ◽  
Current Phase ◽  
Surface Charges ◽  
Shapiro Step ◽  
Gap Opening ◽  
Topological Surface ◽  
Spin Texture

In Josephson junctions, a supercurrent across a nonsuperconducting weak link is carried by electron-hole bound states. Because of the helical spin texture of nondegenerate topological surface states, gapless bound states are established in junctions with topological weak link. These have a characteristic 4π-periodic current phase relation (CΦR) that leads to twice the conventional Shapiro step separation voltage in radio frequency–dependent measurements. In this context, we identify an attenuated first Shapiro step in (Bi0.06Sb0.94)2Te3 (BST) Josephson junctions with AlOx capping layer. We further investigate junctions on narrow, selectively deposited BST nanoribbons, where surface charges are confined to the perimeter of the nanoribbon. Within these junctions, previously identified signatures of gapless bound states are absent. Because of confinement, transverse momentum sub-bands are quantized and a topological gap opening is observed. Surface states within these quantized sub-bands are spin degenerate, which evokes bound states of conventional 2π-periodic CΦR within the BST nanoribbon weak link.

scholarly journals Superconducting topological surface states in the noncentrosymmetric bulk superconductor PbTaSe2

2016 ◽  
Vol 2 (11) ◽  
pp. e1600894 ◽  
Author(s):  
Syu-You Guan ◽  
Peng-Jen Chen ◽  
Ming-Wen Chu ◽  
Raman Sankar ◽  
Fangcheng Chou ◽  
...  
Keyword(s):  
Bound States ◽  
Dirac Point ◽  
Fault Tolerant ◽  
Bulk Material ◽  
Surface States ◽  
Atomic Scale ◽  
Edge States ◽  
Quasi Particle ◽  
Topological Superconductors ◽  
Topological Surface

The search for topological superconductors (TSCs) is one of the most urgent contemporary problems in condensed matter systems. TSCs are characterized by a full superconducting gap in the bulk and topologically protected gapless surface (or edge) states. Within each vortex core of TSCs, there exists the zero-energy Majorana bound states, which are predicted to exhibit non-Abelian statistics and to form the basis of the fault-tolerant quantum computation. To date, no stoichiometric bulk material exhibits the required topological surface states (TSSs) at the Fermi level (EF) combined with fully gapped bulk superconductivity. We report atomic-scale visualization of the TSSs of the noncentrosymmetric fully gapped superconductor PbTaSe2. Using quasi-particle scattering interference imaging, we find two TSSs with a Dirac point atE≅ 1.0 eV, of which the inner TSS and the partial outer TSS crossEF, on the Pb-terminated surface of this fully gapped superconductor. This discovery reveals PbTaSe2as a promising candidate for TSC.

Large Damping Enhancement in Dirac‐Semimetal–Ferromagnetic‐Metal Layered Structures Caused by Topological Surface States

2021 ◽  
pp. 2008411
Author(s):  
Jinjun Ding ◽  
Chuanpu Liu ◽  
Yuejie Zhang ◽  
Vijaysankar Kalappattil ◽  
Rui Yu ◽  
...  
Keyword(s):  
Surface States ◽  
Layered Structures ◽  
Ferromagnetic Metal ◽  
Dirac Semimetal ◽  
Topological Surface

scholarly journals Discovery of a weak topological insulating state and van Hove singularity in triclinic RhBi2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kyungchan Lee ◽  
Gunnar F. Lange ◽  
Lin-Lin Wang ◽  
Brinda Kuthanazhi ◽  
Thaís V. Trevisan ◽  
...  
Keyword(s):  
Time Reversal ◽  
Topological Insulators ◽  
Dirac Point ◽  
Saddle Points ◽  
Surface States ◽  
Van Hove Singularity ◽  
Space Group ◽  
Topological Materials ◽  
Topological Surface ◽  
Optimal Space

AbstractTime reversal symmetric (TRS) invariant topological insulators (TIs) fullfil a paradigmatic role in the field of topological materials, standing at the origin of its development. Apart from TRS protected strong TIs, it was realized early on that more confounding weak topological insulators (WTI) exist. WTIs depend on translational symmetry and exhibit topological surface states only in certain directions making it significantly more difficult to match the experimental success of strong TIs. We here report on the discovery of a WTI state in RhBi2 that belongs to the optimal space group P$$\bar{1}$$ 1 ¯ , which is the only space group where symmetry indicated eigenvalues enumerate all possible invariants due to absence of additional constraining crystalline symmetries. Our ARPES, DFT calculations, and effective model reveal topological surface states with saddle points that are located in the vicinity of a Dirac point resulting in a van Hove singularity (VHS) along the (100) direction close to the Fermi energy (EF). Due to the combination of exotic features, this material offers great potential as a material platform for novel quantum effects.

scholarly journals Andreev bound states in ferromagnet-superconductor nanostructures

2003 ◽  
Vol 387 (1-2) ◽  
pp. 7-12 ◽  
Author(s):  
M. Krawiec ◽  
B.L. Györffy ◽  
J.F. Annett
Keyword(s):  
Bound States ◽  
Andreev Bound States

Fermi level tuning and the robustness of topological surface states against impurity doping in Sn doped Sb2Te2Se

2021 ◽  
Vol 118 (15) ◽  
pp. 154001
Author(s):  
Debarghya Mallick ◽  
Shoubhik Mandal ◽  
R. Ganesan ◽  
P. S. Anil Kumar
Keyword(s):  
Fermi Level ◽  
Surface States ◽  
Impurity Doping ◽  
Topological Surface

scholarly journals 2D weak anti-localization in thin films of the topological semimetal Pd$$_{3}$$Bi$$_{2}$$S$$_{2}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shama ◽  
R. K. Gopal ◽  
Goutam Sheet ◽  
Yogesh Singh
Keyword(s):  
Thin Films ◽  
Phonon Scattering ◽  
Surface States ◽  
Relaxation Mechanism ◽  
Transport Studies ◽  
Bulk Carriers ◽  
Topological Semimetal ◽  
Topological Surface ◽  
First Time ◽  
Electron Phonon Scattering

AbstractPd$$_{3}$$ 3 Bi$$_{2}$$ 2 S$$_{2}$$ 2 (PBS) is a recently proposed topological semimetal candidate. However, evidence for topological surface states have not yet been revealed in transport measurements due to the large mobility of bulk carriers. We report the growth and magneto-transport studies of PBS thin films where the mobility of the bulk carriers is reduced by two orders of magnitude, revealing for the first time, contributions from the 2-dimensional (2D) topological surface states in the observation of the 2D weak anti-localization (WAL) effect in magnetic field and angle dependent conductivity measurements. The magnetotransport data is analysed within the 2D Hikami-Larkin-Nagaoka (HLN) theory. The analysis suggests that multiple conduction channels contribute to the transport. It is also found that the temperature dependence of the dephasing length can’t be explained only by electron-electron scattering and that electron-phonon scattering also contributes to the phase relaxation mechanism in PBS films.

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