Multitype Dirac fermions protected by orthogonal glide symmetries in a noncentrosymmetric system

Xia, Yun; Cai, Xiaochan; Li, Gang

doi:10.1103/physrevb.102.041201

Cited by 7 publications

(4 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, for the glidesymmetry case (T-O-T configuration), the surface states are always two-fold degenerated at the boundaries of surface BZ (Figure 4D). Such band degeneracy is the consequence of glide symmetries [56][57][58], i.e., G x : (x, y, z) → G(−x, y + a/2, z) and G y : (x, y, z) → G(x + a/2, −y, z). The 3D views of surface states with t x 1 are plotted in Figures 4E,F.…”

Section: Tunable Topological Surface States On Different Domain Wallsmentioning

confidence: 99%

Tunable Topological Surface States of Three-Dimensional Acoustic Crystals

Lai

Sun

et al. 2021

Front. Phys.

View full text Add to dashboard Cite

Topological design for band structures of artificial materials such as acoustic crystals provides a powerful tool to manipulate wave propagating in a robust and symmetry-protected way. In this paper, based on the band folding and breaking mechanism by building blocks with acoustic atoms, we construct a three-dimensional topological acoustic crystal with a large complete bandgap. At a mirror-symmetry domain wall, two gapped symmetry and anti-symmetry surface states can be found in the bandgap, originated from two opposite Su-Schrieffer-Heeger chains. Remarkably, by enforcing a glide symmetry on the domain wall, we can tune the original gapped surface states in a gapless fashion at the boundaries of surface Brillouin zone, acting as omnidirectional acoustic quantum spin Hall effect. Our tunable yet straightforward acoustic crystals offer promising potentials in realizing future topological acoustic devices.

show abstract

Section: Tunable Topological Surface States On Different Domain Wallsmentioning

confidence: 99%

Tunable Topological Surface States of Three-Dimensional Acoustic Crystals

Lai

Sun

et al. 2021

Front. Phys.

View full text Add to dashboard Cite

show abstract

“…SG 108 contains a fourfold crossing that is not pinned to a TRIM but to the point P [85]. Due to the presence of mirror symmetries it does not carry a chirality as topological charge.…”

Section: Sg 108mentioning

confidence: 99%

Symmetry-enforced band crossings in tetragonal materials: Dirac and Weyl degeneracies on points, lines, and planes

Hirschmann,

Leonhardt,

Kilic

et al. 2021

Preprint

View full text Add to dashboard Cite

We study the occurrence of symmetry-enforced topological band crossings in tetragonal crystals with strong spin-orbit coupling. By computing the momentum dependence of the symmetry eigenvalues and the global band topology in the entire Brillouin zone, we determine all symmetryenforced band crossings in tetragonal space groups. In particular, we classify all Dirac and Weyl degeneracies on points, lines, and planes, and find a rich variety of topological degeneracies. This includes, among others, double Weyl points, fourfold-double Weyl points, fourfold-quadruple Weyl points, Weyl and Dirac nodal lines, as well as topological nodal planes. For the space groups with symmetry-enforced Weyl points, we determine the minimal number of Weyl points for a given band pair and, remarkably, find that materials in space groups 119 and 120 can have band pairs with only two Weyl points in the entire Brillouin zone. This simplifies the topological responses, which would be useful for device applications. Using the classification of symmetry-enforced band crossings, we perform an extensive database search for candidate materials with tetragonal space groups. Notably, we find that Ba5In4Bi5 and NaSn5 exhibit twofold and fourfold Weyl nodal lines, respectively, which cross the Fermi energy. Hf3Sb and Cs2Tl3 have band pairs with few number of Weyl points near the Fermi energy. Furthermore, we show that Ba3Sn2 has Weyl points with an accordion dispersion and topological nodal planes, while AuBr and Tl4PbSe3 possess Dirac points with hourglass dispersions. For each of these candidate materials we present the ab-initio band structures and discuss possible experimental signatures of the nontrivial band topology.

show abstract

“…In the case of systems with inversion symmetry this effort was facilitated by a general symmetry classification of centrosymmetric Dirac semimetals 26 , which has led to the prediction of a large number of Dirac semimetals with inversion symmetry, including BaAgBi 31 , SrPd 3 O 4 32 and MgTa 2 N 3 33 . Compared to the centrosymmetric variants, Dirac semimetals without inversion symmetry have been much less studied and theoretical predictions of material candidates are comparatively rare [34][35][36][37] . Furthermore, a detailed understanding of the phase diagram of noncentrosymmetric Dirac semimetals, obtained from a derivation and analysis of effective model Hamiltonians, is still lacking, even though the absence of inversion symmetry is expected to give rise to a richer phase diagram.…”

Section: Introductionmentioning

confidence: 99%

Noncentrosymmetric topological Dirac semimetals in three dimensions

Gao,

Strockoz,

Frakulla

et al. 2021

Preprint

View full text Add to dashboard Cite

Topological Dirac semimetals are a class of semimetals that host symmetry-protected Dirac points near the Fermi level, which arise due to a band inversion of the conduction and valence bands. In this work, we study the less explored class of noncentrosymmetric topological Dirac semimetals in three dimensions. We identify the noncentrosymmetric crystallographic point groups required to stabilize fourfold degenerate band crossings and derive model Hamiltonians for all distinct types of band inversions allowed by symmetry. Using these model Hamiltonians, which emphasize the physical nature of the allowed couplings, we establish the generic electronic phase diagram noncentrosymmetric Dirac semimetals and show that it generically includes phases with coexistent Weyl point nodes or Weyl line nodes. In particular, for one specific type of band inversion in sixfold symmetric systems we show that Weyl line nodes are always present. Based on first-principles calculations, we predict that BiPd2O4 is a noncentrosymmetric Dirac semimetal under 20 Gpa pressure and hosts topological type-II Dirac points on the fourfold rotation axis. Furthermore, we propose that the hexagonal polar alloy LiZnSbxBi1−x realizes a Dirac semimetal with coexistent Weyl points. Interestingly, the emergence and location of the Weyl points is highly tunable and can be controlled by the alloy concentration x. More generally, our results not only establish band-inverted noncentrosymmetric systems as a broad and versatile class of topological semimetals, but also provide a framework for studying the quantum nonlinear Hall effect and nonlinear optical properties in the Dirac semimetals.

show abstract

Multitype Dirac fermions protected by orthogonal glide symmetries in a noncentrosymmetric system

Cited by 7 publications

References 44 publications

Tunable Topological Surface States of Three-Dimensional Acoustic Crystals

Tunable Topological Surface States of Three-Dimensional Acoustic Crystals

Symmetry-enforced band crossings in tetragonal materials: Dirac and Weyl degeneracies on points, lines, and planes

Noncentrosymmetric topological Dirac semimetals in three dimensions

Contact Info

Product

Resources

About