Abstract
By means of ab initio band structure methods and model Hamiltonians we investigate the electronic, spin and topological properties of four monopnictides crystallizing in bct structure. We show that the Weyl bands around a WP W1 or W2 possess a strong anisotropy and tilt of the accompanying Dirac cones. These effects are larger for W2 nodes than for W1 ones. The node tilts and positions in energy space significantly influence the DOS of single-particle Weyl excitations. The node anisotropies destroy the conventional picture of (anti)parallel spin and wave vector of a Weyl fermion. This also holds for the Berry curvature around a node, while the monopole charges are independent as integrated quantities. The pairing of the nodes strongly modifies the spin texture and the Berry curvature for wave vectors in between the two nodes. Spin components may change their orientation. Integrals over planes perpendicular to the connection line yield finite Zak phases and winding numbers for planes between the two nodes, thereby indicating the topological character.Graphical abstract
Highlights
All fermions discovered in the menagerie of conventional particles have a finite mass
In this paper we theoretically investigate the anisotropy and tilt of Dirac cones at Weyl points in noncentrosymmetric Weyl semimetals by a combination of ab initio band structure calculations and model Hamiltonians for each Weyl point, whose parameters are fitted to the band-structure results
Since we focus on the low-energy Weyl fermion excitations around the Fermi level, we neglect quasiparticle effects [3], which, in 2D graphene-like crystals, only increase the Fermi velocities by about 10−20% [18,33]
Summary
All fermions discovered in the menagerie of conventional particles have a finite mass. The existence of Weyl fermions as lowenergy electronic excitations was predicted by Herring [4] in the context of electronic band structures of crystals. Such massless quasiparticles have been recently discovered in the so-called Weyl semimetals [5] of the TaAs compound family [6,7,8,9,10].
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