Topological Surface States of Dirac Fermions in n-Bi2Te3 –ySey Thermoelectrics

2019 ◽  
Vol 53 (5) ◽  
pp. 647-651
Author(s):  
L. N. Lukyanova ◽  
I. V. Makarenko ◽  
O. A. Usov ◽  
P. A. Dementev
Keyword(s):  
Surface States ◽  
Dirac Fermions ◽  
Topological Surface

scholarly journals Fermi-crossing Type-II Dirac fermions and topological surface states in NiTe2

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Saumya Mukherjee ◽  
Sung Won Jung ◽  
Sophie F. Weber ◽  
Chunqiang Xu ◽  
Dong Qian ◽  
...  
Keyword(s):  
Surface States ◽  
Dirac Fermions ◽  
Type Ii ◽  
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 Photoemission Spectroscopic Evidence of Multiple Dirac Cones in Superconducting BaSn3

2021 ◽  
Vol 38 (10) ◽  
pp. 107403
Author(s):  
Zhe Huang ◽  
Xianbiao Shi ◽  
Gaoning Zhang ◽  
Zhengtai Liu ◽  
Soohyun Cho ◽  
...  
Keyword(s):  
Surface States ◽  
Photoemission Spectroscopy ◽  
Rotational Axis ◽  
Type I ◽  
Dirac Fermions ◽  
First Principles Calculations ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Topological Quantum ◽  
Topological Surface ◽  
Single Material

Signatures of topological superconductivity (TSC) in superconducting materials with topological nontrivial states prompt intensive researches recently. Utilizing high-resolution angle-resolved photoemission spectroscopy and first-principles calculations, we demonstrate multiple Dirac fermions and surface states in superconductor BaSn3 with a critical transition temperature of about 4.4 K. We predict and then unveil the existence of two pairs of type-I topological Dirac fermions residing on the rotational axis. Type-II Dirac fermions protected by screw axis are confirmed in the same compound. Further calculation for the spin helical texture of the observed surface states originating from the Dirac fermions gives an opportunity for realization of TSC in one single material. Hosting multiple Dirac fermions and topological surface states, the intrinsic superconductor BaSn3 is expected to be a new platform for further investigation of topological quantum materials as well as TSC.

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.

scholarly journals Dimensional crossover and band topology evolution in ultrathin semimetallic NiTe2 films

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Joseph A. Hlevyack ◽  
Liang-Ying Feng ◽  
Meng-Kai Lin ◽  
Rovi Angelo B. Villaos ◽  
Ro-Ya Liu ◽  
...  
Keyword(s):  
Film Thickness ◽  
Ultrathin Films ◽  
Molecular Beam ◽  
Surface States ◽  
Single Layer ◽  
Dirac Fermions ◽  
Dirac Semimetal ◽  
Emergent Phenomena ◽  
Device Applications ◽  
Topological Surface

AbstractNickel ditelluride (NiTe2), a recently discovered Type-II Dirac semimetal with topological Dirac fermions near the Fermi energy, is expected to exhibit strong thickness-mediated electronic tunability and intrinsic two-gap superconductivity in the single-layer limit. Realizing such intriguing phenomena requires the fabrication of ultrathin NiTe2 films and an understanding of the underlying physics that is still under debate. By conducting experimental band mappings of ultrathin films prepared with molecular beam epitaxy, we reveal spectroscopic evidence for the dimensionality crossover of single-crystalline ultrathin NiTe2 films as a function of film thickness. As the film thickness increases from one to five layers, the gap in the conical topological surface states closes. Comparisons of experimental to first-principles results also highlight difficulties in fabricating atomically smooth single-layer NiTe2 films. Our results not only provide further impetus for studying emergent phenomena in NiTe2 but also underscore the limitations of fabricating NiTe2 films for device applications.

scholarly journals Топологические поверхностные состояния фермионов Дирака в термоэлектриках n-Bi-=SUB=-2-=/SUB=-Te-=SUB=-3-y-=/SUB=-Se-=SUB=-y-=/SUB=-

2019 ◽  
Vol 53 (5) ◽  
pp. 654
Author(s):  
Л.Н. Лукьянова ◽  
И.В. Макаренко ◽  
О.А. Усов ◽  
П.А. Дементьев
Keyword(s):  
Dirac Point ◽  
Energy Gap ◽  
Surface States ◽  
Surface Concentration ◽  
Scanning Tunneling ◽  
Fermi Velocity ◽  
Dirac Fermions ◽  
Tunneling Microscopy ◽  
Topological Surface ◽  
Local Distortions

Topological surface states of Dirac fermions in n-Bi2Te3−ySey thermoelectrics L.N. Lukyanova, I.V. Makarenko, O.A. Usov, P.A. Dementev Ioffe Institute, 194021 St. Petersburg, Russia Abstract In n-Bi2Te3 and n-Bi2Te3−ySey thermoelectrics, the surface states of Dirac fermions of the interlayer van der Waals plane (0001) were studied by scanning tunneling microscopy (STM) and spectroscopy. The surface morphology and modulated line profiles of the images in tunneling microscopy is determined by local distortions of the surface electron states density and depend on the composition. The Dirac point ED of the studied compositions is localized in the energy gap, and it shifts to the top of the valence band with increase of Se content in the solid solutions. The dependence between Dirac surface state parameters (the Dirac point position, the Fermi velocity, the fermion surface concentration) and thermoelectric properties (Seebeck coefficient and the power factor) is established for the thermoelectrics studied.

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.

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
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