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 Ultrafast evolution of bulk, surface and surface resonance states in photoexcited $$\hbox {Bi}_{2}\hbox {Te}_{3}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hamoon Hedayat ◽  
Davide Bugini ◽  
Hemian Yi ◽  
Chaoyu Chen ◽  
Xingjiang Zhou ◽  
...  
Keyword(s):  
Surface States ◽  
Photoemission Spectroscopy ◽  
Time Resolved ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Interband Scattering ◽  
Surface Resonance ◽  
Bulk Surface ◽  
Unpolarized Electron ◽  
Topological Surface

AbstractWe use circular dichroism (CD) in time- and angle-resolved photoemission spectroscopy (trARPES) to measure the femtosecond charge dynamics in the topological insulator (TI) $$\hbox {Bi}_{2}\hbox {Te}_{3}$$ Bi 2 Te 3 . We detect clear CD signatures from topological surface states (TSS) and surface resonance (SR) states. In time-resolved measurements, independently from the pump polarization or intensity, the CD shows a dynamics which provides access to the unexplored electronic evolution in unoccupied states of $$\hbox {Bi}_{2}\hbox {Te}_{3}$$ Bi 2 Te 3 . In particular, we are able to disentangle the unpolarized electron dynamics in the bulk states from the spin-textured TSS and SR states on the femtosecond timescale. Our study demonstrates that photoexcitation mainly involves the bulk states and is followed by sub-picosecond transport to the surface. This provides essential details on intra- and interband scattering in the relaxation process of TSS and SR states. Our results reveal the significant role of SRs in the subtle ultrafast interaction between bulk and surface states of TIs.

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.

Recent Advances in Topological Quantum Materials by Angle-Resolved Photoemission Spectroscopy

Matter ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 1114-1141
Author(s):  
Yujie Chen ◽  
Xu Gu ◽  
Yiwei Li ◽  
Xian Du ◽  
Lexian Yang ◽  
...  
Keyword(s):  
Photoemission Spectroscopy ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Recent Advances ◽  
Topological Quantum ◽  
Quantum Materials

scholarly journals Ultrafast Charge Separation in Bilayer WS2/Graphene Heterostructure Revealed by Time- and Angle-Resolved Photoemission Spectroscopy

2021 ◽  
Vol 9 ◽  
Author(s):  
Razvan Krause ◽  
Mariana Chávez-Cervantes ◽  
Sven Aeschlimann ◽  
Stiven Forti ◽  
Filippo Fabbri ◽  
...  
Keyword(s):  
Charge Separation ◽  
Graphene Layer ◽  
Optoelectronic Devices ◽  
Visible Spectral Range ◽  
Band Alignment ◽  
Photoemission Spectroscopy ◽  
Type I ◽  
Type Ii ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Indirect Band Gap

Efficient light harvesting devices need to combine strong absorption in the visible spectral range with efficient ultrafast charge separation. These features commonly occur in novel ultimately thin van der Waals heterostructures with type II band alignment. Recently, ultrafast charge separation was also observed in monolayer WS2/graphene heterostructures with type I band alignment. Here we use time- and angle-resolved photoemission spectroscopy to show that ultrafast charge separation also occurs at the interface between bilayer WS2 and graphene indicating that the indirect band gap of bilayer WS2 does not affect the charge transfer to the graphene layer. The microscopic insights gained in the present study will turn out to be useful for the design of novel optoelectronic devices.

scholarly journals Dirac nodal surfaces and nodal lines in ZrSiS

2019 ◽  
Vol 5 (5) ◽  
pp. eaau6459 ◽  
Author(s):  
B.-B. Fu ◽  
C.-J. Yi ◽  
T.-T. Zhang ◽  
M. Caputo ◽  
J.-Z. Ma ◽  
...  
Keyword(s):  
Photoemission Spectroscopy ◽  
Dirac Fermions ◽  
Fermi Surfaces ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Nodal Lines ◽  
Nodal Points ◽  
Different Dimensions ◽  
Topological Semimetals ◽  
Symmetry Protected ◽  
Nodal Surfaces

Topological semimetals are characterized by symmetry-protected band crossings, which can be preserved in different dimensions in momentum space, forming zero-dimensional nodal points, one-dimensional nodal lines, or even two-dimensional nodal surfaces. Materials harboring nodal points and nodal lines have been experimentally verified, whereas experimental evidence of nodal surfaces is still lacking. Here, using angle-resolved photoemission spectroscopy (ARPES), we reveal the coexistence of Dirac nodal surfaces and nodal lines in the bulk electronic structures of ZrSiS. As compared with previous ARPES studies on ZrSiS, we obtained pure bulk states, which enable us to extract unambiguously intrinsic information of the bulk nodal surfaces and nodal lines. Our results show that the nodal lines are the only feature near the Fermi level and constitute the whole Fermi surfaces. We not only prove that the low-energy quasiparticles in ZrSiS are contributed entirely by Dirac fermions but also experimentally realize the nodal surface in topological semimetals.

scholarly journals Intrinsic magnetic topological insulator phases in the Sb doped MnBi2Te4 bulks and thin flakes

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Bo Chen ◽  
Fucong Fei ◽  
Dongqin Zhang ◽  
Bo Zhang ◽  
Wanling Liu ◽  
...  
Keyword(s):  
First Principles ◽  
Magnetic Order ◽  
Photoemission Spectroscopy ◽  
First Principles Calculations ◽  
New Device ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Potential Applications ◽  
Device Applications ◽  
Physical Phenomena ◽  
Promising Avenue

Abstract Magnetic topological insulators (MTIs) offer a combination of topologically nontrivial characteristics and magnetic order and show promise in terms of potentially interesting physical phenomena such as the quantum anomalous Hall (QAH) effect and topological axion insulating states. However, the understanding of their properties and potential applications have been limited due to a lack of suitable candidates for MTIs. Here, we grow two-dimensional single crystals of Mn(SbxBi(1-x))2Te4 bulk and exfoliate them into thin flakes in order to search for intrinsic MTIs. We perform angle-resolved photoemission spectroscopy, low-temperature transport measurements, and first-principles calculations to investigate the band structure, transport properties, and magnetism of this family of materials, as well as the evolution of their topological properties. We find that there exists an optimized MTI zone in the Mn(SbxBi(1-x))2Te4 phase diagram, which could possibly host a high-temperature QAH phase, offering a promising avenue for new device applications.

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
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