Higher-fold topological excitations in phononic and electronic phases of chiral-type BaXY (X = Pt, Pd; Y= P, As, Sb, Bi) materials: A first-principles investigation Available to Purchase

Non-symmorphic chiral crystals hosting higher-fold fermions and bosons are of great interest due to the recent experimental realizations. The specialty of these higher-fold fermions and bosons is that they possess long Fermi arcs connecting the Brillouin zone boundaries. In this work, using first-principles calculations, we examine the higher-fold topological phases in the phonon spectrum and electronic band structure of ternary chiral crystals BaXY (X = Pt, Pd; Y = P, As, Sb, Bi). Our detailed analysis reveals the symmetry-protected spin-1 Weyl and charge-2 Dirac topological phonon phase in the phonon spectrum. Contrastingly, the electronic states exhibit intriguing fourfold and sixfold fermionic states under spin–orbit coupling. Interestingly, we found the emergence of giant topological surface Fermi arcs in both phonon and electronic phases. Our findings highlight the coexistence of higher-fold topological phases in both the electronic and phononic states in all of the studied ternary chiral crystals, which may serve future topological device applications.