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

Bibhash Paul^1*, Feng-Chuan Chuang^1,2,3,4

¹Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
²Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan
³Center for Theoretical and Computational Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
⁴Department of Physics, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Bibhash Paul, email:bibhashpaul0007@g-mail.nsysu.edu.tw

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 six-fold fermionic states under spin-orbit coupling (SOC). 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.

Keywords: Higher-fold topological states, Spin-1 Weyl, Charge-2 Dirac, Chiral structure, First-principles calculations