Electron and phonon topology in transition metal material TaSi

Abstract: The plethora of multifold quasiparticles in topological materials has led to significant advancements in condensed matter physics, inspiring the investigation for materials that host both electronic and bosonic multifold excitations. In this work, we explore the electronic and phononic properties of TaSi, a non symmorphic chiral topological material crystallizing in space group P 2 1 3 (No. 198). This system exhibits multifold fermions, which are higher spin generalizations of Weyl fermions, protected by the unique crystalline symmetries of the structure. Using first principles calculations, we predict that electronic band possesses fourfold spin 3/2 Rarita Schwinger (RSW) fermions, sixfold excitations (double spin 1), all possessing large Chern numbers C = +4 and Weyl fermions of spin 1/2 with Chern no. -1 in the presence of spin orbit coupling (SOC). Additionally, the phononic band structure hosts chiral bosonic excitations characterized by Chern numbers C = +-2. The coexistence of chiral electronic and bosonic quasiparticles give rise to exotic transport phenomena, rendering the material as promising candidate for future applications in quantum materials, topological electronics, and spintronics.