Multi-fold fermionic and bosonic states in topologically non-trivial Ti3Pd.

The topological properties of the A15-type compound Ti3Pd reveal a complex landscape of multi-fold fermionic and bosonic states, as uncovered through ab initio calculations within the framework of density functional theory (DFT). The electronic band structure shows multi-fold degenerate crossings at the high-symmetry point R near the Fermi level, which evolves into 4-fold and 8-fold degenerate fermionic states upon the introduction of spin-orbit coupling (SOC). Likewise, the phononic band structure features multi-fold degenerate bosonic crossings at the same R point. Topological analysis, including the calculation of 2 invariant and surface states, confirms the non-trivial nature of Ti3Pd. Moreover, both fermionic and bosonic quasiparticles exhibit nodal line features, whose topological non-triviality is further substantiated by Berry phase calculation. This research illuminates the intricate topological framework of Ti3Pd, opening avenues for experimental exploration in the field of topological quantum materials.