Hybrid single-pair charge-2 Weyl semimetals

TL;DR

This paper predicts and verifies a new class of hybrid charge-2 Weyl semimetals with distinct dispersions protected by nonsymmorphic symmetries, featuring unique surface states and potential for experimental exploration.

Contribution

The study introduces a theoretical prediction and first-principles verification of hybrid charge-2 Weyl semimetals with mixed quadratic and linear Weyl nodes, protected by nonsymmorphic symmetries.

Findings

Hybrid charge-2 Weyl nodes with quadratic and linear dispersions are predicted.

Symmetries localize Weyl points at specific Brillouin zone locations.

Surface states span the entire Brillouin zone, aiding experimental detection.

Abstract

Intuitively, the dispersion characteristics of Weyl nodes with opposite charges in single-pair charge-2 Weyl semimetals are the same, quadratic or linear. We theoretically predicted that single-pair hybrid charge-2 Weyl semimetals (the nodes with opposite charges show quadratic Weyl and linear charge-2 Dirac characteristics, respectively) can be protected by specific nonsymmorphic symmetries in spinless systems. Moreover, the symmetries force the pair of Weyl points locate at the center and corners of the first Brillouin zone (FBZ), respectively. Consequently, nontrivial surface states run through the entire FBZ of the system fascinating for future experimental detection and device applications. The hybrid phase is further verified with the help of first-principles calculations for the phonon states in realistic material of Na$_2$Zn$_2$O$_3$. The new phase will not only broaden the understanding of the Weyl semimetals, but also provide an interesting platform to investigate the interaction between the two types of Weyl fermions with different dispersions.