scholarly journals Surface states in Dirac semimetals and topological crystalline insulators

2018 ◽  
Vol 98 (4) ◽  
Author(s):  
Grigory Bednik
Keyword(s):  
Surface States ◽  
Dirac Semimetals ◽  
Topological Crystalline Insulators

scholarly journals Symmetry Indicators and Anomalous Surface States of Topological Crystalline Insulators

2018 ◽  
Vol 8 (3) ◽  
Author(s):  
Eslam Khalaf ◽  
Hoi Chun Po ◽  
Ashvin Vishwanath ◽  
Haruki Watanabe
Keyword(s):  
Surface States ◽  
Anomalous Surface ◽  
Topological Crystalline Insulators

scholarly journals Are the surface Fermi arcs in Dirac semimetals topologically protected?

2016 ◽  
Vol 113 (31) ◽  
pp. 8648-8652 ◽  
Author(s):  
Mehdi Kargarian ◽  
Mohit Randeria ◽  
Yuan-Ming Lu
Keyword(s):  
Chemical Potential ◽  
Surface States ◽  
Quantum Oscillation ◽  
Band Model ◽  
Fermi Surfaces ◽  
Space Groups ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Fermi Arcs ◽  
Anomalous Surface ◽  
Dirac Semimetals

Motivated by recent experiments probing anomalous surface states of Dirac semimetals (DSMs) Na3Bi and Cd3As2, we raise the question posed in the title. We find that, in marked contrast to Weyl semimetals, the gapless surface states of DSMs are not topologically protected in general, except on time-reversal-invariant planes of surface Brillouin zone. We first demonstrate this finding in a minimal four-band model with a pair of Dirac nodes at k=(0,0,±Q), where gapless states on the side surfaces are protected only near kz=0. We then validate our conclusions about the absence of a topological invariant protecting double Fermi arcs in DSMs, using a K-theory analysis for space groups of Na3Bi and Cd3As2. Generically, the arcs deform into a Fermi pocket, similar to the surface states of a topological insulator, and this pocket can merge into the projection of bulk Dirac Fermi surfaces as the chemical potential is varied. We make sharp predictions for the doping dependence of the surface states of a DSM that can be tested by angle-resolved photoemission spectroscopy and quantum oscillation experiments.

scholarly journals Photoelectromagnetic Effect Induced by Terahertz Laser Radiation in Topological Crystalline Insulators Pb1−xSnxTe

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3207
Author(s):  
Alexandra V. Galeeva ◽  
Dmitry A. Belov ◽  
Aleksei S. Kazakov ◽  
Anton V. Ikonnikov ◽  
Alexey I. Artamkin ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Dispersion Relation ◽  
Terahertz Radiation ◽  
Crystallographic Orientation ◽  
Composition Range ◽  
Surface States ◽  
Incident Radiation ◽  
Topological Phase ◽  
Surface Electron ◽  
Topological Crystalline Insulators

Topological crystalline insulators form a class of semiconductors for which surface electron states with the Dirac dispersion relation are formed on surfaces with a certain crystallographic orientation. Pb1−xSnxTe alloys belong to the topological crystalline phase when the SnTe content x exceeds 0.35, while they are in the trivial phase at x < 0.35. For the surface crystallographic orientation (111), the appearance of topologically nontrivial surface states is expected. We studied the photoelectromagnetic (PEM) effect induced by laser terahertz radiation in Pb1−xSnxTe films in the composition range x = (0.11–0.44), with the (111) surface crystallographic orientation. It was found that in the trivial phase, the amplitude of the PEM effect is determined by the power of the incident radiation, while in the topological phase, the amplitude is proportional to the flux of laser radiation quanta. A possible mechanism responsible for the effect observed presumes damping of the thermalization rate of photoexcited electrons in the topological phase and, consequently, prevailing of electron diffusion, compared with energy relaxation.

scholarly journals Discovery of $${\hat{\boldsymbol{C}}}_2$$ rotation anomaly in topological crystalline insulator SrPb

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wenhui Fan ◽  
Simin Nie ◽  
Cuixiang Wang ◽  
Binbin Fu ◽  
Changjiang Yi ◽  
...  
Keyword(s):  
Surface States ◽  
Binary Compound ◽  
Dirac Fermions ◽  
Rotation Symmetry ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Topological Crystalline Insulators ◽  
Topological Crystalline Insulator ◽  
Nontrivial Topology ◽  
Bulk Band

AbstractTopological crystalline insulators (TCIs) are insulating electronic states with nontrivial topology protected by crystalline symmetries. Recently, theory has proposed new classes of TCIs protected by rotation symmetries $$\hat C_n$$ C ̂ n , which have surface rotation anomaly evading the fermion doubling theorem, i.e., n instead of 2n Dirac cones on the surface preserving the rotation symmetry. Here, we report the first realization of the $$\hat C_2$$ C ̂ 2 rotation anomaly in a binary compound SrPb. Our first-principles calculations reveal two massless Dirac fermions protected by the combination of time-reversal symmetry $$\hat T$$ T ̂ and $$\hat C_{2y}$$ C ̂ 2 y on the (010) surface. Using angle-resolved photoemission spectroscopy, we identify two Dirac surface states inside the bulk band gap of SrPb, confirming the $$\hat C_2$$ C ̂ 2 rotation anomaly in the new classes of TCIs. The findings enrich the classification of topological phases, which pave the way for exploring exotic behavior of the new classes of TCIs.

scholarly journals Wallpaper fermions and the nonsymmorphic Dirac insulator

Science ◽  
2018 ◽  
Vol 361 (6399) ◽  
pp. 246-251 ◽  
Author(s):  
Benjamin J. Wieder ◽  
Barry Bradlyn ◽  
Zhijun Wang ◽  
Jennifer Cano ◽  
Youngkuk Kim ◽  
...  
Keyword(s):  
Surface States ◽  
Dirac Fermion ◽  
Space Group ◽  
Insulating Phase ◽  
Topological Crystalline Insulators ◽  
Surface Crystal ◽  
Wallpaper Groups

Materials whose gapless surface states are protected by crystal symmetries include mirror topological crystalline insulators and nonsymmorphic hourglass insulators. There exists only a very limited set of possible surface crystal symmetries, captured by the 17 “wallpaper groups.” Here we show that a consideration of symmetry-allowed band degeneracies in the wallpaper groups can be used to understand previously described topological crystalline insulators and to predict phenomenologically distinct examples. In particular, the two wallpaper groups with multiple glide lines, pgg and p4g, allow for a topological insulating phase whose surface spectrum consists of only a single, fourfold-degenerate, true Dirac fermion, representing an exception to a symmetry-enhanced fermion-doubling theorem. We theoretically predict the presence of this phase in Sr2Pb3 in space group 127 (P4/mbm).

Enhancement of thermoelectric performance via weak disordering of topological crystalline insulators and band convergence by Se alloying in Pb0.5Sn0.5Te1 − xSex

2018 ◽  
Vol 6 (14) ◽  
pp. 5870-5879 ◽  
Author(s):  
Dianta Ginting ◽  
Chan-Chieh Lin ◽  
Gareoung Kim ◽  
Jae Hyun Yun ◽  
Byung-Kyu Yu ◽  
...  
Keyword(s):  
Thermoelectric Materials ◽  
High Performance ◽  
Thermoelectric Performance ◽  
New Strategy ◽  
Dirac Semimetals ◽  
Topological Crystalline Insulators

This research proposes a new strategy for exploring high-performance thermoelectric materials by weak disordering of topological crystalline Dirac semimetals.

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