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 Selective trapping of hexagonally warped topological surface states in a triangular quantum corral

2019 ◽  
Vol 5 (5) ◽  
pp. eaaw3988 ◽  
Author(s):  
Mu Chen ◽  
Ye-Ping Jiang ◽  
Junping Peng ◽  
Huimin Zhang ◽  
Cui-Zu Chang ◽  
...  
Keyword(s):  
Surface Defects ◽  
Three Dimensional ◽  
Surface States ◽  
Real Space ◽  
Dirac Fermions ◽  
Selection Rules ◽  
Potential Barriers ◽  
Topological Surface ◽  
Spin Texture ◽  
Complicated Surface

The surface of a three-dimensional topological insulator (TI) hosts two-dimensional massless Dirac fermions (DFs), the gapless and spin-helical nature of which leads to their high transmission through surface defects or potential barriers. Here, we report the behaviors of topological surface states (TSS) in a triangular quantum corral (TQC) which, unlike a circular corral, is supposed to be totally transparent for DFs. By real-space mapping of the electronic structure of TQCs, both the trapping and detrapping behaviors of the TSS are observed. The selection rules are found to be governed by the geometry and spin texture of the constant energy contour of TSS upon the strong hexagonal warping in Bi2Te3. Our work indicates the extended nature of TSS and elucidates the selection rules of the trapping of TSS in the presence of a complicated surface state structure, giving insights into the effective engineering of DFs in TIs.

Topological surface states protected from backscattering by chiral spin texture

Nature ◽  
2009 ◽  
Vol 460 (7259) ◽  
pp. 1106-1109 ◽  
Author(s):  
Pedram Roushan ◽  
Jungpil Seo ◽  
Colin V. Parker ◽  
Y. S. Hor ◽  
D. Hsieh ◽  
...  
Keyword(s):  
Surface States ◽  
Topological Surface ◽  
Spin Texture

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.

scholarly journals Bilinear magnetoelectric resistance as a probe of three-dimensional spin texture in topological surface states

2018 ◽  
Vol 14 (5) ◽  
pp. 495-499 ◽  
Author(s):  
Pan He ◽  
Steven S.-L. Zhang ◽  
Dapeng Zhu ◽  
Yang Liu ◽  
Yi Wang ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Surface States ◽  
Topological Surface ◽  
Spin Texture

scholarly journals Weyl nodes in periodic structures of superconductors and spin-active materials

2018 ◽  
Vol 376 (2125) ◽  
pp. 20150151
Author(s):  
Ahmet Keles ◽  
Erhai Zhao
Keyword(s):  
Bound States ◽  
Periodic Structures ◽  
Surface States ◽  
Calculated Spectrum ◽  
Active Materials ◽  
Nodal Structure ◽  
Topological Superconductors ◽  
Fermi Arcs ◽  
Spin Texture ◽  
Weyl Fermions

Motivated by recent progress in epitaxial growth of proximity structures of s -wave superconductors (S) and spin-active materials (M), in this paper we show that certain periodic structures of S and M can behave effectively as superconductors with pairs of point nodes, near which the low-energy excitations are Weyl fermions. A simple model, where M is described by a Kronig–Penney potential with both spin–orbit coupling and exchange field, is proposed and solved to obtain the phase diagram of the nodal structure, the spin texture of the Weyl fermions, as well as the zero-energy surface states in the form of open Fermi lines (Fermi arcs). As a second example, a lattice model with alternating layers of S and magnetic Z 2 topological insulators is solved. The calculated spectrum confirms previous predictions of Weyl nodes based on the tunnelling Hamiltonian of Dirac electrons. Our results provide further evidence that periodic structures of S and M are well suited for engineering gapless topological superconductors. This article is part of the theme issue ‘Andreev bound states’.

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.

Sign in / Sign up

Export Citation Format

Share Document