Catalog of maximally charged Weyl points hosting nearly emanating nodal lines in phonon spectra
Dongze Fan, Xiangang Wan, Feng Tang
Abstract
Recently, by exhausting low-energy $k\ifmmode\cdot\else\textperiodcentered\fi{}p$ effective models around all band crossings in the 230 space groups, it was found that the maximal topological charge of the twofold-degenerate Weyl point (WP) is 4 only in the spinless setting. However, such a WP has yet to be realized in phonon spectra of crystalline material. In this paper, we perform high-throughput database calculations for charge-4 Weyl phonons in nonmagnetic materials and select the most ideal charge-4 WP per high-symmetry point allowing charge-4 phonons in each material. Moreover, the $k\ifmmode\cdot\else\textperiodcentered\fi{}p$ effective model around the charge-4 WP should be expanded to at least third order, and by explicitly solving for nodal lines, four nearly straight nodal lines carrying ``quasiquantized'' Berry phase can be anticipated. We select the three best candidates, BaPtSi, SrIrP, and ${\mathrm{Ta}}_{3}{\mathrm{Al}}_{2}\mathrm{C}$, to verify the predicted nearly nodal lines and also showcase the phonon surface states associated with the charge-4 WP and the coexisting spin-1 WPs and charge-2 Dirac points. Our results provide a platform of materials with diverse chemical compositions hosting charge-4 WPs, expected to assist experimentalists in selecting suitable materials for further study.