scholarly journals Insight into the Topological Nodal Line Metal YB2 with Large Linear Energy Range: A First-Principles Study

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3841
Author(s):  
Yang Li ◽  
Jihong Xia ◽  
Rabah Khenata ◽  
Minquan Kuang
Keyword(s):  
Energy Range ◽  
First Principles ◽  
Phonon Dispersion ◽  
Nodal Line ◽  
Spin Orbit Coupling ◽  
Metallic Material ◽  
Nodal Lines ◽  
Band Crossing ◽  
Crossing Point ◽  
Insight Into

The presence of one-dimensional (1D) nodal lines, which are formed by band crossing points along a line in the momentum space of materials, is accompanied by several interesting features. However, in order to facilitate experimental detection of the band crossing point signatures, the materials must possess a large linear energy range around the band crossing points. In this work, we focused on a topological metal, YB2, with phase stability and a P6/mmm space group, and studied the phonon dispersion, electronic structure, and topological nodal line signatures via first principles. The computed results show that YB2 is a metallic material with one pair of closed nodal lines in the kz = 0 plane. Importantly, around the band crossing points, a large linear energy range in excess of 2 eV was observed, which was rarely reported in previous reports that focus on linear-crossing materials. Furthermore, YB2 has the following advantages: (1) An absence of a virtual frequency for phonon dispersion, (2) an obvious nontrivial surface state around the band crossing point, and (3) small spin–orbit coupling-induced gaps for the band crossing points.

scholarly journals Perfect Topological Metal CrB2: A One-Dimensional (1D) Nodal Line, a Zero-Dimensional (0D) Triply Degenerate Point, and a Large Linear Energy Range

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4321
Author(s):  
Yang Li ◽  
Jihong Xia ◽  
Rabah Khenata ◽  
Minquan Kuang
Keyword(s):  
Energy Range ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Nodal Lines ◽  
Topological Materials ◽  
Experimental Detection ◽  
Triple Points ◽  
Band Crossing ◽  
Topological Metal

Topological materials with band-crossing points exhibit interesting electronic characteristics and have special applications in electronic devices. However, to further facilitate the experimental detection of the signatures of these band crossings, topological materials with a large linear energy range around the band-crossing points need to be found, which is challenging. Here, via first-principle approaches, we report that the previously prepared P6/mmm-type CrB2 material is a topological metal with one pair of 1D band-crossing points, that is, nodal lines, in the kz= 0 plane, and one pair of 0D band-crossing points, that is, triple points, along the A–Γ–A’ paths. Remarkably, around these band-crossing points, a large linear energy range (larger than 1 eV) was found and the value was much larger than that found in previously studied materials with a similar linear crossing. The pair of nodal lines showed obvious surface states, which show promise for experimental detection. The effect of the spin–orbit coupling on the band-crossing points was examined and the gaps induced by spin–orbit coupling were found to be up to 69 meV. This material was shown to be phase stable in theory and was synthesized in experiments, and is therefore a potential material for use in investigating nodal lines and triple points.

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.

Predicted Weyl fermions in magnetic GdBi and GdSb

2017 ◽  
Vol 31 (29) ◽  
pp. 1750217 ◽  
Author(s):  
Zhi Li ◽  
Dan-Dan Xu ◽  
Shu-Yu Ning ◽  
Haibin Su ◽  
Toshiaki Iitaka ◽  
...  
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Topological Charge ◽  
Local Density ◽  
Chiral Anomaly ◽  
First Principles Calculations ◽  
Rotation Symmetry ◽  
Band Crossing ◽  
Crossing Point ◽  
Weyl Fermions

Motivated by the chiral anomaly steering negative longitudinal magnetoresistance in GdBiPt under external magnetic field, we studied the electronic structures of GdBi with paramagnetism, antiferromagnetism and ferromagnetism by first-principles calculations with modified Becke and Johnson local density approximation plus Hubbard [Formula: see text]. Our calculated results reveal that paramagnetic GdBi is semiconducting, while the antiferromagnetic GdBi is a topological nontrivial compensation metal. We also predict the presence of a pair of Weyl fermions in ferromagnetic GdBi and GdSb. The band crossing along the direction of magnetization is protected by the fourfold rotation symmetry, and the topological charge associating with each [Formula: see text] band crossing point is [Formula: see text].

Topological phonons and electronic structure of Li2BaSi class of semimetals

2021 ◽  
Author(s):  
Vineet Kumar Sharma ◽  
Birender Singh ◽  
Anan Bari Sarkar ◽  
Mayanak Kumar Gupta ◽  
Ranjan Mittal ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Transport Properties ◽  
Careful Analysis ◽  
Nodal Line ◽  
Theoretical Modelling ◽  
Spin Orbit Coupling ◽  
Band Inversion ◽  
Device Applications ◽  
Band Crossing ◽  
Nontrivial Topology

Abstract Extension of the topological concepts to the Bosonic systems has led to the prediction of topological phonons in materials. Here we discuss the topological phonons and electronic structure of Li2BaX (X = Si, Ge, Sn, and Pb) materials using first-principles theoretical modelling. A careful analysis of the phonon spectrum of Li2BaX reveals an optical mode inversion with the formation of nodal line states in the Brillouin zone. Our electronic structure results reveal a double band inversion at the Γ point with the formation of inner nodal-chain states in the absence of spin-orbit coupling (SOC). Inclusion of the SOC opens a materials-dependent gap at the band crossing points and transitions the system into a trivial insulator state. We also discuss the lattice thermal conductivity and transport properties of Li2BaX materials. Our results show that coexisting phonon and electron nontrivial topology with robust transport properties would make Li2BaX materials appealing for device applications.

scholarly journals Obvious Surface States Connecting to the Projected Triple Points in NaCl’s Phonon Dispersion

2021 ◽  
Vol 9 ◽  
Author(s):  
Li Zhang ◽  
Fang Fang ◽  
Lixin Cheng ◽  
Huiming Lin ◽  
Kai Wang
Keyword(s):  
Computer Technology ◽  
Triple Point ◽  
First Principles ◽  
Phonon Dispersion ◽  
Surface States ◽  
Theoretical Chemistry ◽  
First Principles Calculations ◽  
Nodal Lines ◽  
Topological Materials ◽  
Speed And Accuracy

With the development of computer technology and theoretical chemistry, the speed and accuracy of first-principles calculations have significantly improved. Using first-principles calculations to predict new topological materials is a hot research topic in theoretical and computational chemistry. In this work, we focus on a well-known material, sodium chloride (NaCl), and propose that the triple point (TP), quadratic contact triple point (QCTP), linear and quadratic nodal lines can be found in the phonon dispersion of NaCl with Fm3¯ m type structure. More importantly, we propose that the clear surface states connected to the projected TP and QCTP are visible on the (001) surface. It is hoped that further experimental investigation and verification for these properties as mentioned above.

Mechanical, Electronic, and Optical Properties of β-B6O: First-Principles Calculations

2017 ◽  
Vol 72 (9) ◽  
pp. 805-810 ◽  
Author(s):  
Ruike Yang ◽  
Shaowei Ma ◽  
Qun Wei ◽  
Zheng Du
Keyword(s):  
Optical Properties ◽  
Energy Range ◽  
First Principles ◽  
Phonon Dispersion ◽  
Hard Material ◽  
Generalized Gradient ◽  
Covalent Bonds ◽  
Electronic And Optical Properties ◽  
A Value ◽  
The Stability

AbstractThe mechanical, electronic, and optical properties of β-B6O are calculated by first-principles. The structural optimization and all properties are calculated by the method of generalized gradient approximation – Perdew, Burke and Ernzerhof (PBE). The hardness of β-B6O is 39 GPa under a pressure of 0 GPa, which indicates that it belongs to a hard material. The band gap is indirect with a value of 1.836 eV, showing that β-B6O is a semiconductor. The research of the electron localization function shows that the bonds of β-B6O are covalent bonds, which can increase the stability of the compound. The phonon dispersion curves present the dynamical stability of β-B6O under pressures of 0 and 50 GPa. The optical properties of β-B6O are also calculated. In the energy range from 0 to 18 eV, β-B6O presents high reflectivity; it has a strong absorption in the energy range from 3 to 18 eV. The refractive index results show that light propagates through the β-B6O in a difficult manner in the energy range from 6.9 to 16.5 eV. In addition, the energy of the plasma frequency for β-B6O is 16.6 eV and the peak value of the loss function is 13.6. These properties provide the basis for the development and application of β-B6O.

scholarly journals First-Principles Calculation for the Influence of C and O on the Mechanical Properties of γ-TiAl Alloy at High Temperature

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 262
Author(s):  
Jiahua Wang ◽  
Yong Lu ◽  
Xiaohong Shao
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
First Principles ◽  
Tial Alloy ◽  
Mechanical Performance ◽  
Phonon Dispersion ◽  
External Pressure ◽  
First Principles Calculation ◽  
Insight Into ◽  
Phonon Dispersion Relations

The elastic constants of temperature dependence, thermal expansion coefficient and phonon dispersion relations of γ-TiAl doped with C/O have been investigated using first-principles calculations in order to gain insight into the mechanical performance of γ-TiAl in cases of high temperature. This study shows that γ-TiAl maintains stability at high temperatures introduced by C or O atoms. Importantly, the hardness increases and retains excellent resistance to external pressure. The results indicate that even if the TiAl alloy is doped with C or O atoms, it can also exhibit excellent mechanical properties at a high temperature.

scholarly journals Kramers nodal line metals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ying-Ming Xie ◽  
Xue-Jian Gao ◽  
Xiao Yan Xu ◽  
Cheng-Ping Zhang ◽  
Jin-Xin Hu ◽  
...  
Keyword(s):  
Time Reversal ◽  
Nodal Line ◽  
Spin Orbit Coupling ◽  
Fermi Surfaces ◽  
Nodal Lines ◽  
New Class ◽  
Topological Materials ◽  
Weyl Semimetals ◽  
Chiral Crystals ◽  
Torus Type

AbstractRecently, it was pointed out that all chiral crystals with spin-orbit coupling (SOC) can be Kramers Weyl semimetals (KWSs) which possess Weyl points pinned at time-reversal invariant momenta. In this work, we show that all achiral non-centrosymmetric materials with SOC can be a new class of topological materials, which we term Kramers nodal line metals (KNLMs). In KNLMs, there are doubly degenerate lines, which we call Kramers nodal lines (KNLs), connecting time-reversal invariant momenta. The KNLs create two types of Fermi surfaces, namely, the spindle torus type and the octdong type. Interestingly, all the electrons on octdong Fermi surfaces are described by two-dimensional massless Dirac Hamiltonians. These materials support quantized optical conductance in thin films. We further show that KNLMs can be regarded as parent states of KWSs. Therefore, we conclude that all non-centrosymmetric metals with SOC are topological, as they can be either KWSs or KNLMs.

scholarly journals Various Nodal Lines in P63/mmc-type TiTe Topological Metal and its (001) Surface State

2021 ◽  
Vol 9 ◽  
Author(s):  
Peng Lin ◽  
Fang Fang ◽  
Li Zhang ◽  
Yang Li ◽  
Kai Wang
Keyword(s):  
Surface States ◽  
Strain Engineering ◽  
Nodal Line ◽  
Type I ◽  
Chemical Doping ◽  
Spin Orbit Coupling ◽  
Nodal Lines ◽  
Hybrid Type ◽  
Two Hybrid ◽  
Topological Metal

Searching for existing topological materials is a hot topic in quantum and computational chemistry. This study uncovers P63/mmc type TiTe compound—an existing material—is a newly discovered topological metal that hosts the various type of nodal line states. Different nodal line states normally exhibit different properties; they may have their individual applications. We report that TiTe hosts I, II, and hybrid type nodal line (NL) states at its ground state without chemical doping and strain engineering effects. Specifically, two type I NLs, two hybrid-type NLs, and one Γ—centered type II NL can be found in the kz = 0 plane. Moreover, the spin-orbit coupling induced gaps for these NLs are very small and within acceptable limits. The surface states of the TiTe (001) plane were determined to provide strong evidence for the appearance of the three types of NLs in TiTe. We also provide a reference for the data of the dynamic and mechanical properties of TiTe. We expect that the proposed NL states in TiTe can be obtained in future experiments.

scholarly journals Computational Simulation of the Electronic State Transition in the Ternary Hexagonal Compound BaAgBi

2021 ◽  
Vol 9 ◽  
Author(s):  
Yu Chang ◽  
Xin Wang ◽  
Sanggyun Na ◽  
Weiwei Zhang
Keyword(s):  
Theoretical Calculations ◽  
Computational Simulation ◽  
Tight Binding ◽  
Surface States ◽  
Nodal Line ◽  
Spin Orbit Coupling ◽  
State Behavior ◽  
Nodal Lines ◽  
Topological Features ◽  
Wide Energy

Topological properties in metals or semimetals have sparked tremendous scientific interest in quantum chemistry because of their exotic surface state behavior. The current research focus is still on discovering ideal topological metal material candidates. We propose a ternary compound with a hexagonal crystal structure, BaAgBi, which was discovered to exhibit two Weyl nodal ring states around the Fermi energy level without the spin–orbit coupling (SOC) effect using theoretical calculations. When the SOC effect is considered, the topological phases transform into two Dirac nodal line states, and their locations also shift from the Weyl nodal rings. The surface states of both the Weyl nodal ring and Dirac nodal lines were calculated on the (001) surface projection using a tight-binding Hamiltonian, and clear drumhead states were observed, with large spatial distribution areas and wide energy variation ranges. These topological features in BaAgBi can be very beneficial for experimental detection, inspiring further experimental investigation.

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