Observation of a Dirac nodal line in 
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Takane, Daichi; Souma, S.; Nakayama, K.; Nakamura, Takechika; Oinuma, Hikaru; Hori, Kentaro; Horiba, Koji; Kumigashira, Hiroshi; Kimura, Noriaki; Takahashi, Takashi; Sato, Takafumi

doi:10.1103/physrevb.98.041105

Cited by 36 publications

(22 citation statements)

References 51 publications

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“…At the H point, the Dirac crossing is found 5.4 eV below the Fermi level, i.e., its energy changes by more than 5.5 eV between the K and H points of the Brillouin zone. A Diraclike crossing occurs at the Brillouin zone corner for each value of the out-of-plane momentum, thus forming a so-called Dirac nodal line along the K-H direction, which has recently been experimentally observed using soft x-ray ARPES [22]. Furthermore, the three-dimensional nature of the p z orbitals enables a larger degree of hybridization with the Al orbitals.…”

Section: A Bulk Statesmentioning

confidence: 87%

Surface and bulk electronic structure of aluminium diboride

et al. 2020

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We report a combined experimental and theoretical study of the surface and bulk electronic structure of aluminium diboride, a nonsuperconducting sister compound of the superconductor MgB 2. We perform angleresolved photoemission measurements with variable photon energy, and compare them to density functional theory calculations to disentangle the surface and bulk contributions to the measured spectra. Aluminium diboride is known to be aluminium deficient, Al 1−δ B 2 , which would be expected to lead to a hole doping as compared to the nominally stoichimoetric compound. Nonetheless, we find that the bulk σ states, which mediate superconductivity in MgB 2 , remain more than 600 meV below the Fermi level. However, we also observe σ states originating from the boron terminated surface, with an order of magnitude smaller binding energy of 70 meV, and demonstrate how surface hole-doping can bring these across the Fermi level.

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Section: A Bulk Statesmentioning

confidence: 87%

Surface and bulk electronic structure of aluminium diboride

et al. 2020

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“…Soon after, other nodal line materials in the absence of spin-orbital interaction were predicted, such as alkalineearth compounds AX 2 (A = Ca, Sr, Ba; X = Si, Ge, Sn) [171], the CaP 3 family of materials [172,173], some of which are experimentally demonstrated, such as CaCdSn [174] and Mg 3 Bi 3 [169] (Figure 7b). Furthermore, topological semimetals can be classified into two types according to the tilting degree of the fermion cone.…”

Section: A Electronic Crystalsmentioning

confidence: 98%

Nodal lines in momentum space: topological invariants and recent realizations in photonic and other systems

Park¹,

Gao²,

Zhang³

et al. 2022

Preprint

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Topological insulators constitute one of the most intriguing phenomena in modern condensed matter theory. The unique and exotic properties of topological states of matter allow for unidirectional gapless electron transport and extremely accurate measurements of the Hall conductivity. Recently, new topological effects occurring at Dirac/Weyl points have been better understood and demonstrated using artificial materials such as photonic and phononic crystals, metamaterials and electrical circuits. In comparison, the topological properties of nodal lines, which are one-dimensional degeneracies in momentum space, remain less explored. Here, we explain the theoretical concept of topological nodal lines and review recent and ongoing progress using artificial materials. The review includes recent demonstrations of non-Abelian topological charges of nodal lines in momentum space and examples of nodal lines realized in photonic and other systems. Finally, we will address the challenges involved in both experimental demonstration and theoretical understanding of topological nodal lines.

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“…We emphasize that similar type-II nodal lines have also been reported in AA stacked graphite, the hightemperature superconductor MgB 2 and it's iso-structural counterparts like AlB 2 . [54][55][56] We present the Fermi surface of Pt 2 HgSe 3 in Fig. 3(d) with unique electron and hole pockets.…”

Section: Bulk Electronic Structure and Topological Invariantsmentioning

confidence: 99%

Saddle-point Van Hove singularity and dual topological state in Pt2HgSe3

et al. 2019

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Saddle-point van Hove singularities in the topological surface states are interesting because they can provide a new pathway for accessing exotic correlated phenomena in topological materials. Here, based on first-principles calculations combined with a k · p model Hamiltonian analysis, we show that the layered platinum mineral jacutingaite (Pt2HgSe3) harbours saddle-like topological surface states with associated van Hove singularities. Pt2HgSe3 is shown to host two distinct types of nodal lines without spin-orbit coupling (SOC) which are protected by combined inversion (I) and timereversal (T ) symmetries. Switching on the SOC gaps out the nodal lines and drives the system into a topological insulator state with nonzero weak topological invariant Z2 = (0; 001) and mirror Chern number nM = 2. Surface states on the naturally cleaved (001) surface are found to be nontrivial with a unique saddle-like energy dispersion with type II van Hove singularities. We also discuss how modulating the crystal structure can drive Pt2HgSe3 into a Dirac semimetal state with a pair of Dirac points. Our results indicate that Pt2HgSe3 is an ideal candidate material for exploring the properties of topological insulators with saddle-like surface states.

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Observation of a Dirac nodal line in AlB2

Cited by 36 publications

References 51 publications

Surface and bulk electronic structure of aluminium diboride

Surface and bulk electronic structure of aluminium diboride

Nodal lines in momentum space: topological invariants and recent realizations in photonic and other systems

Saddle-point Van Hove singularity and dual topological state in Pt2HgSe3

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