The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Jihong Xia - One of the best experts on this subject based on the ideXlab platform.
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cubic scpd topological metal closed Nodal line spin orbit coupling induced triply degenerate Nodal Point dirac Nodal Point transition
Results in physics, 2020Co-Authors: Dong Zhang, Jihong Xia, Rabah Khenata, Minquan KuangAbstract:Abstract The presence of Nodal Points (NPs) and Nodal lines (NLs) in the momentum space of topological materials is accompanied by many interesting properties. In this study, we predicted that an existing material ScPd with Pm 3 ¯ m-type structure would have closed NLs in the kx/y/z = 0 planes and one pair of triply degenerate NPs (TNPs) along the R-M-R′ paths, respectively, when the spin–orbit coupling (SOC) effect is not taken into consideration. Obvious nontrivial surface states were found around band-crossing Points A, B, and C, which can be seen as good evidence for the topological signatures of ScPd metal. When the SOC effect was added, a TNP–Dirac NP (DNP) transition appeared along the R-M-R′ paths. Also, the band-crossing Points belonging to the closed NL in the kx/y/z = 0 planes were gapped by the induction of SOC. However, the SOC-induced gaps were very small ( X ¯ Point. This material has been proved to be dynamically and mechanically stable in theory and has been synthesized experimentally; it is therefore a good target for future investigation of the properties of NLs and NPs, and their relationship.
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Cubic Hafnium Nitride: A Novel Topological Semimetal Hosting a 0-Dimensional (0-D) Nodal Point and a 1-D Topological Nodal Ring.
Frontiers in chemistry, 2020Co-Authors: Jihong XiaAbstract:Very recently, topological semimetals with nontrivial band crossing and associated topological surface states have received widespread attention. Various types of topological semimetals, including Nodal Point semimetals, Nodal line semimetals, and Nodal surface semimetals, have been predicted from first principles. In absence of spin-orbit coupling (SOC) effect, we propose that cubic-type hafnium nitride (HfN) with a Pm3¯m space group is a novel topological semimetal hosting a rare 0-D triple Nodal Point and a 1-D topological Nodal ring. More importantly, the interesting 0-D and 1-D topological states all occur near the Fermi level, and these topological states are not disturbed by other extraneous bands. When the SOC effect is taken into consideration, 0-D triple Nodal Point was gapped and a new 0-D topological element, namely, Dirac Point appears along Γ-R path. Finally, the dynamical and mechanical stabilities of this semimetal and its associated mechanical properties are discussed in order to provide a reference for future investigations. Our work promises that HfN can serve as a superior topological semimetal with high stability, excellent mechanical properties, and rich topological states.
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Cubic ScPd topological metal: Closed Nodal line, spin-orbit coupling-induced triply degenerate Nodal Point–Dirac Nodal Point transition
Results in Physics, 2020Co-Authors: Dong Zhang, Jihong Xia, Rabah Khenata, Minquan KuangAbstract:Abstract The presence of Nodal Points (NPs) and Nodal lines (NLs) in the momentum space of topological materials is accompanied by many interesting properties. In this study, we predicted that an existing material ScPd with Pm 3 ¯ m-type structure would have closed NLs in the kx/y/z = 0 planes and one pair of triply degenerate NPs (TNPs) along the R-M-R′ paths, respectively, when the spin–orbit coupling (SOC) effect is not taken into consideration. Obvious nontrivial surface states were found around band-crossing Points A, B, and C, which can be seen as good evidence for the topological signatures of ScPd metal. When the SOC effect was added, a TNP–Dirac NP (DNP) transition appeared along the R-M-R′ paths. Also, the band-crossing Points belonging to the closed NL in the kx/y/z = 0 planes were gapped by the induction of SOC. However, the SOC-induced gaps were very small ( X ¯ Point. This material has been proved to be dynamically and mechanically stable in theory and has been synthesized experimentally; it is therefore a good target for future investigation of the properties of NLs and NPs, and their relationship.
Gang Zhang - One of the best experts on this subject based on the ideXlab platform.
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Diverse topological states in a ternary NdAsPd compound
Journal of Materials Chemistry C, 2020Co-Authors: Tie Yang, Guangqian Ding, Zhenxiang Cheng, Xiaotian Wang, Gang ZhangAbstract:The exploration of topological states in materials is currently focused on metals and semimetals, and their linear band crossing features various topological states, including a Nodal Point, Nodal line and Nodal surface. Based on first principles calculations, we have predicted a ternary NdAsPd compound that exhibits multiple topological states of a type-II Nodal ring, triply degenerate Nodal Point and Nodal surface states in the absence of spin orbit coupling (SOC) effects. Its band formation mechanism has been analyzed and the corresponding nontrivial drumhead surface and Fermi arc have been confirmed. Under the consideration of SOC, these topological states evolve into a type-II Nodal Point and type-I Nodal line. The remarkable topological diversity in the present material is very rare and can serve as a promising platform upon which to study the rich fermionic states in a single material.
Piet W. Brouwer - One of the best experts on this subject based on the ideXlab platform.
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Disorder correction to the minimal conductance of a Nodal-Point semimetal
Physical Review B, 2020Co-Authors: Zheng Shi, Björn Sbierski, Piet W. BrouwerAbstract:We consider the disorder-induced correction to the minimal conductance of an anisotropic two-dimensional Dirac node or a three-dimensional Weyl node. An analytical expression is derived for the correction $\ensuremath{\delta}G$ to the conductance of a finite-size sample by an arbitrary potential, without taking the disorder average, in second-order perturbation theory. Considering a generic model of a short-range disorder potential, this result is used to compute the probability distribution $P(\ensuremath{\delta}G)$, which is compared to the numerically exact distribution obtained using the scattering matrix approach. We show that $P(\ensuremath{\delta}G)$ is Gaussian when the sample has a large width-to-length ratio and study how the expectation value, the standard deviation, and the probability of finding $\ensuremath{\delta}Gl0$ depend on the anisotropy of the dispersion.
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Quantum Transport of Disordered Weyl Semimetals at the Nodal Point
Physical review letters, 2014Co-Authors: Björn Sbierski, Gregor Pohl, Emil J. Bergholtz, Piet W. BrouwerAbstract:Weyl semimetals are paradigmatic topological gapless phases in three dimensions. We here address the effect of disorder on charge transport in Weyl semimetals. For a single Weyl node with energy at the degeneracy Point and without interactions, theory predicts the existence of a critical disorder strength beyond which the density of states takes on a nonzero value. Predictions for the conductivity are divergent, however. In this work, we present a numerical study of transport properties for a disordered Weyl cone at zero energy. For weak disorder, our results are consistent with a renormalization group flow towards an attractive pseudoballistic fixed Point with zero conductivity and a scale-independent conductance; for stronger disorder, diffusive behavior is reached. We identify the Fano factor as a signature that discriminates between these two regimes.
Yugui Yao - One of the best experts on this subject based on the ideXlab platform.
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Type-II topological metals
Frontiers of Physics, 2020Co-Authors: Yugui Yao, Shengyuan A. YangAbstract:Topological metals (TMs) are a kind of special metallic materials, which feature nontrivial band crossings near the Fermi energy, giving rise to peculiar quasiparticle excitations. TMs can be classified based on the characteristics of these band crossings. For example, according to the dimensionality of the crossing, TMs can be classified into Nodal-Point, Nodal-line, and Nodal-surface metals. Another important property is the type of dispersion. According to degree of the tilt of the local dispersion around the crossing, we have type-I and type-II dispersions. This leads to significant distinctions in the physical properties of the materials, owing to their contrasting Fermi surface topologies. In this article, we briefly review the recent advances in this research direction, focusing on the concepts, the physical properties, and the material realizations of the type-II Nodal-Point and Nodal-line TMs.
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Weyl Nodal Point-Line Fermion in Ferromagnetic Eu5Bi3.
The journal of physical chemistry letters, 2019Co-Authors: Wei Guo, Yugui YaoAbstract:On the basis of ab initio calculations and a low-energy effective k· p model, we propose a Weyl Nodal Point-line (WNPL) fermion, composed of 0D Weyl Points and a 1D Weyl Nodal line, in the ferromagnetic material Eu5Bi3. In the absence of spin-orbital coupling (SOC), the spin-up bands host a pair of triply degenerate Points together with a bird-cage-like node structure. In the presence of SOC with (001) magnetization, each triplet Point splits into a double Weyl Point and a single Weyl Point accompanied by two Nodal rings, forming two sets of WNPL fermions near the Fermi level. The novel properties of the WNPL fermion are explored by revealing the unusual Berry curvature field and demonstrating the pinned chiral surface states with exotic Fermi arcs. Our work offers new ideas for exploring novel topological semimetal states with diverse band-crossing dimensions and provides a candidate for future experimental realization.
Yu-jie Zhou - One of the best experts on this subject based on the ideXlab platform.
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Principle of the rotation of small particles around a Nodal Point of strip in flexural vibration
Sensors and Actuators A: Physical, 2012Co-Authors: Xiao-bo Zhu, Yu-jie ZhouAbstract:Abstract In this report, we investigate the principle of rotation of micro particles around a Nodal Point of metal strip in flexural vibration, by experimental measurement and theoretical analysis. It is experimentally found that local travelling waves with the same travelling direction may exist along the circles centered at the Nodal Point of flexural vibration, and these local travelling waves can drive a particle cluster agglomerated at the Nodal Point to rotate. The acoustic radiation force, acoustic viscous force and acoustic streaming are excluded from the possible driving force by measuring and comparing the revolution speed of particle cluster in the normal environment of 1 atm and 25 °C and in a glass vessel of 0.04 atm and 25 °C. The generation of local travelling waves is related to the non-uniformity of vibration distribution along the width direction of vibration excitation part of metal strip. The physical principle obtained can well explain the measured relationships between the revolution speed and rotating particle number, and between the revolution speed and vibration displacement amplitude. There is slip between the rotating particles and vibrating surface, and air drag has little contribution to the particle rotation.
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Principle of the rotation of small particles around a Nodal Point of flexurally vibrating strip
2011 Symposium on Piezoelectricity Acoustic Waves and Device Applications (SPAWDA), 2011Co-Authors: Jun-hui Hu, Yu-jie Zhou, Hua-qing LiAbstract:In this report, we investigate the principle of rotation of micro particles around a Nodal Point of metal strip in flexural vibration, by experimental measurement and theoretical analysis. It is experimentally found that travelling wave may exist along the circles centered at the Nodal Point, and the travelling wave can drive a particle cluster agglomerated at the Nodal Point to rotate. The acoustic radiation force, acoustic viscous force and acoustic streaming are excluded from the possible driving force by measuring and comparing the revolution speed of particle cluster in the normal environment of 1 atm and 25°C and in a glass vessel of 0.04 atm and 25°C. The physical principle obtained can well explain the measured relationships between the revolution speed and vibration displacement amplitude. Also, it is found that there is slide between the rotating particles and vibrating surface.