Weak antilocalization in HgTe quantum wells and topological surface states: Massive versus massless Dirac fermions

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.

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Photoemission Spectroscopic Evidence of Multiple Dirac Cones in Superconducting BaSn3

Chinese Physics Letters ◽

10.1088/0256-307x/38/10/107403 ◽

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.

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

Science Advances ◽

10.1126/sciadv.aaw3988 ◽

2019 ◽

Vol 5 (5) ◽

pp. eaaw3988 ◽

Cited By ~ 1

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.

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Robust topological surface states in Sb2Te3layers as seen from the weak antilocalization effect

Physical Review B ◽

10.1103/physrevb.86.125137 ◽

2012 ◽

Vol 86 (12) ◽

Cited By ~ 54

Author(s):

Y. Takagaki ◽

A. Giussani ◽

K. Perumal ◽

R. Calarco ◽

K.-J. Friedland

Keyword(s):

Surface States ◽

Weak Antilocalization ◽

Topological Surface

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Dimensional crossover and band topology evolution in ultrathin semimetallic NiTe2 films

npj 2D Materials and Applications ◽

10.1038/s41699-021-00218-z ◽

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.

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Weak antilocalization effect due to topological surface states in Bi2Se2.1Te0.9

Journal of Applied Physics ◽

10.1063/1.4997947 ◽

2017 ◽

Vol 122 (14) ◽

pp. 145901 ◽

Cited By ~ 5

Author(s):

K. Shrestha ◽

D. Graf ◽

V. Marinova ◽

B. Lorenz ◽

C. W. Chu

Keyword(s):

Surface States ◽

Weak Antilocalization ◽

Topological Surface

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

Физика и техника полупроводников ◽

10.21883/ftp.2019.05.47557.15 ◽

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.

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