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 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 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 de Haas-van Alphen effect of correlated Dirac states in kagome metal Fe3Sn2

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Linda Ye ◽  
Mun K. Chan ◽  
Ross D. McDonald ◽  
David Graf ◽  
Mingu Kang ◽  
...  
Keyword(s):  
Electronic States ◽  
Spin Orbit Coupling ◽  
Dirac Fermions ◽  
Two Dimensional ◽  
Fermi Surfaces ◽  
Berry Curvature ◽  
Effective Masses ◽  
Topological Materials ◽  
Geometric Frustration ◽  
Highly Correlated

Abstract Primarily considered a medium of geometric frustration, there has been a growing recognition of the kagome network as a harbor of lattice-borne topological electronic phases. In this study we report the observation of magnetoquantum de Haas-van Alphen oscillations of the ferromagnetic kagome lattice metal Fe3Sn2. We observe a pair of quasi-two-dimensional Fermi surfaces arising from bulk massive Dirac states and show that these band areas and effective masses are systematically modulated by the rotation of the ferromagnetic moment. Combined with measurements of Berry curvature induced Hall conductivity, our observations suggest that the ferromagnetic Dirac fermions in Fe3Sn2 are subject to intrinsic spin-orbit coupling in the d electron sector which is likely of Kane-Mele type. Our results provide insights for spintronic manipulation of magnetic topological electronic states and pathways to realizing further highly correlated topological materials from the lattice perspective.

scholarly journals Kramers Weyl semimetals as quantum solenoids and their applications in spin-orbit torque devices

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Wen-Yu He ◽  
Xiao Yan Xu ◽  
K. T. Law
Keyword(s):  
Time Reversal ◽  
Perpendicular Magnetic Anisotropy ◽  
Spin Orbit ◽  
Longitudinal Magnetization ◽  
Spin Magnetization ◽  
Weyl Semimetal ◽  
Electric Control ◽  
Lattice Symmetry ◽  
Weyl Semimetals ◽  
Chiral Crystals

AbstractKramers Weyl semimetals are Weyl semimetals that have Weyl points pinned at the time reversal invariant momenta. Recently it has been discovered that all chiral crystals host Weyl points at time reversal invariant momenta, so metals with chiral lattice symmetry all belong to the category of Kramers Weyl semimetals. In this work, we show that due to the chiral lattice symmetry, Kramers Weyl semimetals have the unique longitudinal magnetoelectric effect in which the charge current induced spin and orbital magnetization is parallel to the direction of the current. This feature allows Kramers Weyl semimetals to act as nanoscale quantum solenoids with both orbital and spin magnetization. As the moving electrons of Kramers Weyl semimetal can generate longitudinal magnetization, Kramers Weyl semimetals can be used for new designs of spin-orbit torque devices with all electric control of magnetization switching for magnets with perpendicular magnetic anisotropy.

scholarly journals Thermodynamics and transport of holographic nodal line semimetals

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Ronnie Rodgers ◽  
Enea Mauri ◽  
Umut Gürsoy ◽  
Henk T.C. Stoof
Keyword(s):  
Lorentz Invariance ◽  
Transport Coefficients ◽  
Low Frequency ◽  
Nodal Line ◽  
Spectral Functions ◽  
Fermi Surfaces ◽  
Nodal Lines ◽  
Dirac Semimetal ◽  
Energy And Momentum ◽  
The Continuum

Abstract We study various thermodynamic and transport properties of a holographic model of a nodal line semimetal (NLSM) at finite temperature, including the quantum phase transition to a topologically trivial phase, with Dirac semimetal-like conductivity. At zero temperature, composite fermion spectral functions obtained from holography are known to exhibit multiple Fermi surfaces. Similarly, for the holographic NLSM we observe multiple nodal lines instead of just one. We show, however, that as the temperature is raised these nodal lines broaden and disappear into the continuum one by one, so there is a finite range of temperatures for which there is only a single nodal line visible in the spectrum. We compute several transport coefficients in the holographic NLSM as a function of temperature, namely the charge and thermal conductivities, and the shear viscosities. By adding a new non-linear coupling to the model we are able to control the low frequency limit of the electrical conductivity in the direction orthogonal to the plane of the nodal line, allowing us to better match the conductivity of real NLSMs. The boundary quantum field theory is anisotropic and therefore has explicitly broken Lorentz invariance, which leads to a stress tensor that is not symmetric. This has important consequences for the energy and momentum transport: the thermal conductivity at vanishing charge density is not simply fixed by a Ward identity, and there are a much larger number of independent shear viscosities than in a Lorentz-invariant system.

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.

scholarly journals Topological semimetal in honeycomb lattice LnSI

2017 ◽  
Vol 114 (40) ◽  
pp. 10596-10600 ◽  
Author(s):  
Simin Nie ◽  
Gang Xu ◽  
Fritz B. Prinz ◽  
Shou-cheng Zhang
Keyword(s):  
Condensed Matter ◽  
Surface States ◽  
Nodal Line ◽  
Honeycomb Lattice ◽  
Nodal Lines ◽  
Weyl Semimetal ◽  
The Standard Model ◽  
Weyl Semimetals ◽  
Topological Semimetals ◽  
The Right

Recognized as elementary particles in the standard model, Weyl fermions in condensed matter have received growing attention. However, most of the previously reported Weyl semimetals exhibit rather complicated electronic structures that, in turn, may have raised questions regarding the underlying physics. Here, we report promising topological phases that can be realized in specific honeycomb lattices, including ideal Weyl semimetal structures, 3D strong topological insulators, and nodal-line semimetal configurations. In particular, we highlight a semimetal featuring both Weyl nodes and nodal lines. Guided by this model, we showed that GdSI, the long-perceived ideal Weyl semimetal, has two pairs of Weyl nodes residing at the Fermi level and that LuSI (YSI) is a 3D strong topological insulator with the right-handed helical surface states. Our work provides a mechanism to study topological semimetals and proposes a platform for exploring the physics of Weyl semimetals as well as related device designs.

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 Double-bowl state in photonic Dirac nodal line semimetal

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Mengying Hu ◽  
Ye Zhang ◽  
Xi Jiang ◽  
Tong Qiao ◽  
Qiang Wang ◽  
...  
Keyword(s):  
Surface States ◽  
Nodal Line ◽  
Electronic Systems ◽  
Nodal Lines ◽  
Spectrum Range ◽  
The Past ◽  
Topological Materials ◽  
Classical Waves ◽  
Topological Semimetals ◽  
Polarized Surface

AbstractThe past decade has seen a proliferation of topological materials for both insulators and semimetals in electronic systems and classical waves. Topological semimetals exhibit topologically protected band degeneracies, such as nodal points and nodal lines. Dirac nodal line semimetals (DNLS), which own four-fold line degeneracy, have drawn particular attention. DNLSs have been studied in electronic systems but there is no photonic DNLS. Here in this work, we provide a new mechanism, which is unique for photonic systems to investigate a stringent photonic DNLS. When truncated, the photonic DNLS exhibits double-bowl states (DBS), which comprise two sets of perpendicularly polarized surface states. In sharp contrast to nondegenerate surface states in other photonic systems, here the two sets of surface states are almost degenerate over the whole-spectrum range. The DBS and the bulk Dirac nodal ring (DNR) dispersion along the relevant directions, are experimentally resolved.

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