Three-Dimensional Crystalline Modification of Graphene in all-sp2 Hexagonal Lattices with or without Topological Nodal Lines

2019 ◽  
Vol 10 (10) ◽  
pp. 2515-2521 ◽  
Author(s):  
Jian-Tao Wang ◽  
Yuting Qian ◽  
Hongming Weng ◽  
Enge Wang ◽  
Changfeng Chen
Keyword(s):  
Three Dimensional ◽  
Crystalline Modification ◽  
Nodal Lines

scholarly journals Cobalt-based magnetic Weyl semimetals with high-thermodynamic stabilities

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Wei Luo ◽  
Yuma Nakamura ◽  
Jinseon Park ◽  
Mina Yoon
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Interlayer Coupling ◽  
First Principles Calculation ◽  
Optimization Approach ◽  
Binding Model ◽  
Nodal Lines ◽  
Weyl Semimetal ◽  
Topological Quantum ◽  
First Time

AbstractRecent experiments identified Co3Sn2S2 as the first magnetic Weyl semimetal (MWSM). Using first-principles calculation with a global optimization approach, we explore the structural stabilities and topological electronic properties of cobalt (Co)-based shandite and alloys, Co3MM’X2 (M/M’ = Ge, Sn, Pb, X = S, Se, Te), and identify stable structures with different Weyl phases. Using a tight-binding model, for the first time, we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers, while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms, Sn, Ge, and Pb. The Co3SnPbS2 alloy exhibits two distinguished topological phases, depending on the relative positions of the Sn and Pb atoms: a three-dimensional quantum anomalous Hall metal, and a MWSM phase with anomalous Hall conductivity (~1290 Ω−1 cm−1) that is larger than that of Co2Sn2S2. Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.

scholarly journals Synthesis, crystal structure and Hirshfeld analysis of a new crystalline modification of the radical ion salt octamethylenetetrathiafulvalenium triiodide (OMTTF)I3

2018 ◽  
Vol 74 (11) ◽  
pp. 1547-1552
Author(s):  
Adriano Bof de Oliveira ◽  
Johannes Beck ◽  
Jörg Daniels
Keyword(s):  
Positive Charge ◽  
Three Dimensional ◽  
Radical Cations ◽  
Inversion Symmetry ◽  
Formula Unit ◽  
Crystalline Modification ◽  
Asymmetric Unit ◽  
Dimensional Network ◽  
Hirshfeld Analysis ◽  
Centrosymmetric Dimers

The reaction between 4,5,6,7-tetrahydro-2-(4,5,6,7-tetrahydro-1,3-benzodithiol-2-ylidene)-1,3-benzodithiole (common name: 4,4′,5,5′,6,6′,7,7′-octahydrodibenzotetrathiafulvalene, OMTTF) and an excess of iodine in tetrahydrofuran (THF) yielded the respective radical organic polyiodide salt, C14H16S4 +·I3 −. The asymmetric unit contains one and a half formula unit of both the cation and the anion, with the half-ions completed through inversion symmetry. The (OMTTF^\bullet+) positive charge can be assigned by the bond distances and the planar structure of the C2S2C=CS2C2 central fragment. In the crystal, trimers of triiodide anions are connected through secondary intermolecular I...I interactions into almost linear I9 3− polyanions. The non-centrosymmetric OMTTF radical cations are linked by S...S interactions into centrosymmetric dimers, while the centrosymmetric OMTTF cations remain as discrete units. The (OMTTF^\bullet+) radical cations and the triiodide anions are linked by weak C—H...I and C—H...S interactions into a three-dimensional network. This work reports the fourth crystalline modification of the C14H16S4^\bullet+·I3 − salt. The three previous modifications were obtained from a mixture of acetonitrile and toluene [Konarev et al. (2005). Synth. Met. 151, 231–238].

Single-component molecular conductor [Pt(dmdt)2]—a three-dimensional ambient-pressure molecular Dirac electron system

2019 ◽  
Vol 55 (23) ◽  
pp. 3327-3330 ◽  
Author(s):  
Biao Zhou ◽  
Shoji Ishibashi ◽  
Tatsuru Ishii ◽  
Takahiko Sekine ◽  
Ryosuke Takehara ◽  
...  
Keyword(s):  
Ambient Pressure ◽  
Three Dimensional ◽  
Electron System ◽  
Single Component ◽  
Nodal Lines ◽  
Molecular Conductor ◽  
System P ◽  
Dirac Electron

[Pt(dmdt)2], an air-stable single-component molecular conductor, contains massless Dirac electrons and carries Dirac nodal lines at ambient pressure.

scholarly journals Engineering Topological Nodal Line Semimetals in Rashba Spin-Orbit Coupled Atomic Chains

2019 ◽  
Vol 4 (1) ◽  
pp. 25 ◽  
Author(s):  
Paola Gentile ◽  
Vittorio Benvenuto ◽  
Carmine Ortix ◽  
Canio Noce ◽  
Mario Cuoco
Keyword(s):  
Three Dimensional ◽  
Nodal Line ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Atomic Chain ◽  
Nodal Lines ◽  
Rashba Spin ◽  
Charge Potential ◽  
Atomic Chains ◽  
Two Phases

In this paper, we study an atomic chain in the presence of modulated charge potential and modulated Rashba spin-orbit coupling (RSOC) of equal periods. We show that for commensurate periodicities, λ = 4 n with integer n, the three-dimensional synthetic space obtained by sliding the two phases of the charge potential and RSOC features a topological nodal-line semimetal protected by an anti-unitary particle-hole symmetry. The location and shape of the nodal lines strongly depend on the relative amplitude between the charge potential and RSOC.

scholarly journals Crystalline symmetry-protected non-trivial topology in prototype compound BaAl4

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Kefeng Wang ◽  
Ryo Mori ◽  
Zhijun Wang ◽  
Limin Wang ◽  
Jonathan Han Son Ma ◽  
...  
Keyword(s):  
Building Block ◽  
High Temperature Superconductivity ◽  
Point Group ◽  
Three Dimensional ◽  
Group Symmetry ◽  
Rotational Axis ◽  
Strongly Correlated Electron ◽  
Linear Dispersion ◽  
Dirac Spectrum ◽  
Nodal Lines

AbstractThe BaAl4 prototype crystal structure is the most populous of all structure types, and is the building block for a diverse set of sub-structures including the famous ThCr2Si2 family that hosts high-temperature superconductivity and numerous magnetic and strongly correlated electron systems. The MA4 family of materials (M = Sr, Ba, Eu; A = Al, Ga, In) themselves present an intriguing set of ground states including charge and spin orders, but have largely been considered as uninteresting metals. We predict the exemplary compound BaAl4 to harbor a three-dimensional Dirac spectrum with non-trivial topology and possible nodal lines crossing the Brillouin zone, wherein one pair of semi-Dirac points with linear dispersion along the kz direction and quadratic dispersion along the kx/ky direction resides on the rotational axis with C4v point group symmetry. An extremely large, unsaturating positive magnetoresistance in BaAl4 despite an uncompensated band structure is revealed, and quantum oscillations and angle-resolved photoemission spectroscopy measurements confirm the predicted multiband semimetal structure with pockets of Dirac holes and a Van Hove singularity (VHS) remarkably consistent with the theoretical prediction. We thus present BaAl4 as a topological semimetal, casting its prototype status into a role as a building block for a vast array of topological materials.

Time-reversal-breaking Weyl nodal lines in two-dimensional A3C2 (A = Ti, Zr, Hf) intrinsically ferromagnetic materials with high Curie temperature

Nanoscale ◽  
2021 ◽  
Author(s):  
Feng Zhou ◽  
Ying Liu ◽  
Minquan KUANG ◽  
Peng Wang ◽  
Jianhua WANG ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Time Reversal ◽  
Three Dimensional ◽  
Ferromagnetic Materials ◽  
High Curie Temperature ◽  
Two Dimensional ◽  
Nodal Lines ◽  
Spin Polarized

Most materials that feature nontrivial topological band topology are spin-degenerate and three dimensional, strongly restricting them from application in spintronic nanodevices. Hence, two-dimensional (2D) intrinsically spin-polarized systems with rich topological...

Dislocation lines in the hyperbolic umbilic diffraction catastrophe

2006 ◽  
Vol 462 (2072) ◽  
pp. 2299-2313 ◽  
Author(s):  
J.F Nye
Keyword(s):  
Diffraction Pattern ◽  
Cross Section ◽  
Focal Plane ◽  
Dislocation Line ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Optical Vortices ◽  
Nodal Lines ◽  
Wave Interference ◽  
A Chain

The three-dimensional pattern of the hyperbolic umbilic diffraction catastrophe is computed from an integral representation. A detailed description is given of the geometrical arrangement of the wave dislocation lines (optical vortices) on which the diffraction pattern is based. From a crossed grid of nodal lines in the focal plane, two bundles of dislocation lines spring out symmetrically into the regions of 4-wave interference. Each dislocation line then follows a chain of curved segments which approximate successive steps along lattice vectors in the space group Fmmm . The result is a bundle of helices of non-circular cross-section that gradually straighten out until, far from the focal plane, they become the dislocations of the Pearcey diffraction pattern for the cusp catastrophe. A new phenomenon is the multiple puncturing of the caustic surface by a series of helical dislocations.

scholarly journals Two-dimensional higher-order topology in monolayer graphdiyne

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Eunwoo Lee ◽  
Rokyeon Kim ◽  
Junyeong Ahn ◽  
Bohm-Jung Yang
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Higher Order ◽  
Order Topology ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Charge Accumulation ◽  
Binding Model ◽  
Nodal Lines ◽  
Bulk Band

AbstractBased on first-principles calculations and tight-binding model analysis, we propose monolayer graphdiyne as a candidate material for a two-dimensional higher-order topological insulator protected by inversion symmetry. Despite the absence of chiral symmetry, the higher-order topology of monolayer graphdiyne is manifested in the filling anomaly and charge accumulation at two corners. Although its low energy band structure can be properly described by the tight-binding Hamiltonian constructed by using only the pz orbital of each atom, the corresponding bulk band topology is trivial. The nontrivial bulk topology can be correctly captured only when the contribution from the core levels derived from px,y and s orbitals are included, which is further confirmed by the Wilson loop calculations. We also show that the higher-order band topology of a monolayer graphdyine gives rise to the nontrivial band topology of the corresponding three-dimensional material, ABC-stacked graphdiyne, which hosts monopole nodal lines and hinge states.

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