Coexistence of triple nodal points, nodal links, and unusual flat bands in intermetallic APd3 ( A=Pb , Sn)

Abstract

We investigate the electronic structure and several properties, and topological character, of the cubic time-reversal invariant intermetallic compounds PbPd3 and SnPd3 using density functional theory based methods. These compounds have a dispersionless band along the Γ − X line, forming the top of the Pd 4d bands and lying within a few meV of the Fermi level EF . Effects of the flat band on transport and optical properties have been inspected by varying the doping concentration treated with the virtual crystal approximation for substitution on the Pb site. In the absence of spin-orbit coupling (SOC), we find triple nodal points and three-dimensional nodal loops, which are known to lead to surface bands and drumhead states, respectively, which we discuss for PbPd3. SOC removes degeneracy in most of the zone, providing a topological index Z2=1 on the kz = 0 plane that indicates a topological character on that plane. The isovalent and isostructural compound SnPd3 shows only minor differences in its electronic structures, so it is expected to display similar electronic, transport, and topological properties.PACS numbers:

Catalogue of Flat-Band Stoichiometric Materials

“…• Pd 3 Pb [ICSD 42600, SG 221 (P m 3m)] was studied theoretically in Ref. [93] and experimentally by Shubnikov-de Haas oscillations in Ref. [94], pointing toward a flat-band semimetal.…”

Topological Nodal Line Electrides: Realization of an Ideal Nodal Line State Nearly Immune from Spin–Orbit Coupling

“…21,22 Currently, most realistic NLSs are proposed in materials where the inversion (P ) symmetry and the time reversal (T ) symmetry coexist, such as graphene networks, 11,12 Cu 3 PdN, 23,24 CaAgAs, 25 AX 2 (A = Ca, Sr, Ba; X = Si, Ge, Sn), 26 ZrSiS, [27][28][29] CaTe, 30 some elemental metals, [31][32][33] Mg 3 Bi 2 , 34 CaP 3 , 35 MB 2 (M = Sc, Ti, V, Zr, Hf, Nb, Ta), 36,37 Ca 2 As, 38 Li 2 BaSi materials, 39 and so on. [40][41][42][43][44][45][46][47][48] It is well known that for a spinless system, a local symmetry P T is enough to protect a nodal line, for which a general effective Hamiltonian may be expressed as: 11,49 H 0 (k) = (m − k 2 )τ z s 0 + k z τ x s 0 ,…”

Observation of superconductivity in the pressurized Weyl-semimetal candidate TaIrTe4

“…As a ternary variant of WTe 2 , TaIrTe 4 crystallizes in an orthorhombic unit cell and can be viewed as a cell-doubling derivative. Thus, it is proposed to be a candidate of type-II WSM 20,21,22,53 , hosting a combination of twelve Weyl points and two Dirac nodal rings in the Brillouin zone [53][54][55][56][57] , and displaying a non-saturating magnetoresistance effect 53,58 .…”