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 Searching for a promising topological Dirac nodal-line semimetal by angle resolved photoemission spectroscopy

2021 ◽  
Author(s):  
Zhengwang Cheng ◽  
Zhilong Hu ◽  
Shaojian Li ◽  
Xinguo Ma ◽  
Zhifeng Liu ◽  
...  
Keyword(s):  
Band Structure ◽  
Heterogeneous Catalysts ◽  
Nodal Line ◽  
Photoemission Spectroscopy ◽  
High Symmetry ◽  
Dirac Fermions ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Topological Semimetals ◽  
Valence Bands ◽  
Band Crossing

Abstract Topological semimetals, in which conduction and valence bands cross each other at either discrete points or along a closed loop with symmetry protected in the momentum space, exhibited great potential in applications of optical devices as well as heterogeneous catalysts or antiferromagnetic spintronics, especially when the crossing points/lines matches Fermi level (EF). It is intriguing to find the “ideal” topological semimetal material, in which has a band structure with Dirac band-crossing located at EF without intersected by other extraneous bands. Here, by using angle resolved photoemission spectroscopy (ARPES), we investigate the band structure of the so-called “square-net” topological material ZrGeS. The Brillouin zone (BZ) mapping shows the Fermi surface (FS) of ZrGeS is composed by a diamond-shaped nodal line loop at the center of BZ and small electron-like Fermi pockets around X point. The Dirac nodal line band-crossing located right at EF, and shows clearly the linear Dirac band dispersions within a large energy range >1.5 eV below EF, without intersected with other bands. The obtained Fermi velocities and effective masses along Γ-X, Γ-M and M-X high symmetry directions were 4.5 ~ 5.9 eV•Å and 0 ~ 0.50 me, revealing an anisotropic electronic property. Our results suggest that ZrGeS, as a promising topological nodal line semimetal (TNLSM), could provide a promising platform to investigate the Dirac-fermions related physics and the applications of topological devising.

scholarly journals High-frequency rectifiers based on type-II Dirac fermions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Libo Zhang ◽  
Zhiqingzi Chen ◽  
Kaixuan Zhang ◽  
Lin Wang ◽  
Huang Xu ◽  
...  
Keyword(s):  
High Frequency ◽  
Dynamic Range ◽  
High Sensitivity ◽  
High Dynamic Range ◽  
Anisotropy Ratio ◽  
Dirac Fermions ◽  
Topological States ◽  
Topological Semimetals ◽  
Polarized Surface ◽  
Symmetry Protected

AbstractThe advent of topological semimetals enables the exploitation of symmetry-protected topological phenomena and quantized transport. Here, we present homogeneous rectifiers, converting high-frequency electromagnetic energy into direct current, based on low-energy Dirac fermions of topological semimetal-NiTe2, with state-of-the-art efficiency already in the first implementation. Explicitly, these devices display room-temperature photosensitivity as high as 251 mA W−1 at 0.3 THz in an unbiased mode, with a photocurrent anisotropy ratio of 22, originating from the interplay between the spin-polarized surface and bulk states. Device performances in terms of broadband operation, high dynamic range, as well as their high sensitivity, validate the immense potential and unique advantages associated to the control of nonequilibrium gapless topological states via built-in electric field, electromagnetic polarization and symmetry breaking in topological semimetals. These findings pave the way for the exploitation of topological phase of matter for high-frequency operations in polarization-sensitive sensing, communications and imaging.

scholarly journals Symmetry-protected nodal points and nodal lines in magnetic materials

2021 ◽  
Vol 103 (24) ◽  
Author(s):  
Jian Yang ◽  
Chen Fang ◽  
Zheng-Xin Liu
Keyword(s):  
Magnetic Materials ◽  
Nodal Lines ◽  
Nodal Points ◽  
Symmetry Protected

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 Observation of a topological nodal surface and its surface-state arcs in an artificial acoustic crystal

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yihao Yang ◽  
Jian-ping Xia ◽  
Hong-xiang Sun ◽  
Yong Ge ◽  
Ding Jia ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Surface States ◽  
Field Measurements ◽  
Wave System ◽  
Nodal Surface ◽  
Nodal Lines ◽  
Nodal Points ◽  
Higher Dimensional ◽  
Classical Wave ◽  
Nodal Surfaces

AbstractThree-dimensional (3D) gapless topological phases can be classified by the dimensionality of the band degeneracies, including zero-dimensional (0D) nodal points, one-dimensional (1D) nodal lines, and two-dimensional (2D) nodal surfaces. Both nodal points and nodal lines have been realized recently in photonics and acoustics. However, a nodal surface has never been observed in any classical-wave system. Here, we report on the experimental observation of a twofold symmetry-enforced nodal surface in a 3D chiral acoustic crystal. In particular, the demonstrated nodal surface carries a topological charge of 2, constituting the first realization of a higher-dimensional topologically-charged band degeneracy. Using direct acoustic field measurements, we observe the projected nodal surface and its Fermi-arc-like surface states and demonstrate topologically-induced robustness of the surface states against disorders. This discovery of a higher-dimensional topologically-charged band degeneracy paves the way toward further explorations of the physics and applications of new topological semimetal phases.

scholarly journals Electronic structure and signature of Tomonaga–Luttinger liquid state in epitaxial CoSb1−x nanoribbons

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Rui Lou ◽  
Minyinan Lei ◽  
Wenjun Ding ◽  
Wentao Yang ◽  
Xiaoyang Chen ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Luttinger Liquid ◽  
Spectral Weight ◽  
Photoemission Spectroscopy ◽  
Strong Correlations ◽  
Fermi Surfaces ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Temperature Scaling ◽  
Interfacial Charge

AbstractRecently, monolayer CoSb/SrTiO3 has been proposed as a candidate harboring interfacial superconductivity in analogy with monolayer FeSe/SrTiO3. Experimentally, while the CoSb-based compounds manifesting as nanowires and thin films have been realized on SrTiO3 substrates, serving as a rich playground, their electronic structures are still unknown and yet to be resolved. Here, we have fabricated CoSb1−x nanoribbons with quasi-one-dimensional stripes on SrTiO3(001) substrates using molecular beam epitaxy and investigated the electronic structure by in situ angle-resolved photoemission spectroscopy. Straight Fermi surfaces without lateral dispersions are observed. CoSb1−x/SrTiO3 is slightly hole doped, where the interfacial charge transfer is opposite to that in monolayer FeSe/SrTiO3. The spectral weight near the Fermi level exhibits power-law-like suppression and obeys a universal temperature scaling, serving as the signature of Tomonaga–Luttinger liquid (TLL) state. The obtained TLL parameter of ~0.21 shows the underlying strong correlations. Our results not only suggest CoSb1−x nanoribbon as a representative TLL system but also provide clues for further investigations on the CoSb-related interface.

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