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 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 Magnetizing topological surface states of Bi2Se3 with a CrI3 monolayer

2019 ◽  
Vol 5 (5) ◽  
pp. eaaw1874 ◽  
Author(s):  
Yusheng Hou ◽  
Jeongwoo Kim ◽  
Ruqian Wu
Keyword(s):  
Density Functional ◽  
Topological Insulators ◽  
Dirac Point ◽  
Surface States ◽  
Anomalous Hall Effect ◽  
Spin Splitting ◽  
Topological Feature ◽  
Topological Parameters ◽  
General Rules ◽  
Topological Surface

To magnetize surfaces of topological insulators without damaging their topological feature is a crucial step for the realization of the quantum anomalous Hall effect (QAHE) and remains as a challenging task. Through density functional calculations, we found that adsorption of a semiconducting two-dimensional van der Waals (2D-vdW) ferromagnetic CrI3 monolayer can create a sizable spin splitting at the Dirac point of the topological surface states of Bi2Se3 films. Furthermore, general rules that connect different quantum and topological parameters are established through model analyses. This work provides a useful guideline for the realization of QAHE at high temperatures in heterostructures of 2D-vdW magnetic monolayers and topological insulators.

scholarly journals Topological surface states and Dirac point tuning in ternary topological insulators

2012 ◽  
Vol 85 (23) ◽  
Author(s):  
M. Neupane ◽  
S.-Y. Xu ◽  
L. A. Wray ◽  
A. Petersen ◽  
R. Shankar ◽  
...  
Keyword(s):  
Topological Insulators ◽  
Dirac Point ◽  
Surface States ◽  
Topological Surface

scholarly journals Термоэлектрические и гальваномагнитные свойства слоистых пленок n-Bi-=SUB=-2-x-=/SUB=-Sb-=SUB=-x-=/SUB=-Te-=SUB=-3-y-=/SUB=-Se-=SUB=-y-=/SUB=-

2019 ◽  
Vol 53 (5) ◽  
pp. 626
Author(s):  
Л.Н. Лукьянова ◽  
О.А. Усов ◽  
М.П. Волков
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Low Temperatures ◽  
Bulk Material ◽  
Surface States ◽  
Dirac Fermions ◽  
Thermoelectric Efficiency ◽  
Strong Magnetic Fields ◽  
Topological Surface ◽  
Magnetoresistance Oscillations

n nanostructured layered films of topological thermoelectrics n-Bi2−xSbxTe3−y Sey , thermoelectric properties in the temperature range of 4.2−300K and magnetoresistance oscillations in strong magnetic fields at low temperatures were studied. It is shown that thermoelectric efficiency in the layered n-Bi2−xSbxTe3−y Sey films increases as compared with bulk material due to both an increase in the Seebeck coefficient at the temperatures below room one, and a decrease in thermal conductivity and weakening of its temperature dependence. From the analysis of magnetoresistance oscillations, the parameters of topological surface states of Dirac fermions were determined and their influence on thermoelectric properties was estimated.

scholarly journals Platform of chiral Majorana edge modes and its quantum transport phenomena

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
James Jun He ◽  
Tian Liang ◽  
Yukio Tanaka ◽  
Naoto Nagaosa
Keyword(s):  
Quantum Transport ◽  
Bound States ◽  
Majorana Fermions ◽  
Two Dimensional ◽  
Quasi Particle ◽  
One Dimensional ◽  
Solid States ◽  
Topological Superconductors ◽  
Wide Range ◽  
Majorana Modes

AbstractMajorana fermions, as electronic quasi-particle modes in solid states, have been under the focus of research due to their exotic physical properties. While the evidence of Majorana fermions as zero-dimensional bound states has been well established, the existence of one-dimensional Majorana modes is still under debate. The main reason is that the current theoretical proposals of platforms supporting such states are very challenging experimentally. Here, we propose a method to create two-dimensional topological superconductors with a heterostructure of ferromagnet, topological insulator thin film and superconductor. We show that such a system supports one-dimensional chiral Majorana edge modes in a wide range of parameters which is readily achievable in experiments. We further propose a new transport measurement to detect these modes.

scholarly journals Strongly correlated superconductor with polytypic 3D Dirac points

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Sergey Borisenko ◽  
Volodymyr Bezguba ◽  
Alexander Fedorov ◽  
Yevhen Kushnirenko ◽  
Vladimir Voroshnin ◽  
...  
Keyword(s):  
Fermi Level ◽  
Density Functional ◽  
Energy Gap ◽  
Surface States ◽  
Flat Band ◽  
Type I ◽  
Exact Matching ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Topological Superconductors ◽  
Topological Surface

Abstract Topological superconductors should be able to provide essential ingredients for quantum computing, but are very challenging to realize. Spin–orbit interaction in iron-based superconductors opens the energy gap between the p-states of pnictogen and d-states of iron very close to the Fermi level, and such p-states have been recently experimentally detected. Density-functional theory predicts existence of topological surface states within this gap in FeTe1−xSex making it an attractive candidate material. Here we use synchrotron-based angle-resolved photoemission spectroscopy and band structure calculations to demonstrate that FeTe1−xSex (x = 0.45) is a superconducting 3D Dirac semimetal hosting type-I and type-II Dirac points and that its electronic structure remains topologically trivial. We show that the inverted band gap in FeTe1−xSex can possibly be realized by further increase of Te content, but strong correlations reduce it to a sub-meV size, making the experimental detection of this gap and corresponding topological surface states very challenging, not to mention exact matching with the Fermi level. On the other hand, the p–d and d–d interactions are responsible for the formation of extremely flat band at the Fermi level pointing to its intimate relation with the mechanism of high-Tc superconductivity in IBS.

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