Pairing of multiple types of topological phononic quasiparticles in chiral crystal Pt3I8

Abstract

Chiral crystals have recently attracted considerable attention in condensed matter physics owing to their intriguing physical properties. In this work, we perform first-principles calculations combined with symmetry analysis to explore topological phononic quasiparticles in the chiral crystal Pt3I8. Our results reveal that the phonon spectrum of Pt3I8 hosts a rich assortment of topological quasiparticles, including charge-1 and charge-2 Weyl points, charge-2 Dirac points, and nodal surfaces. Remarkably, these quasiparticles emerge in a variety of distinctive pairing configurations, such as a Weyl point with topological charge +2 paired with a Dirac point of charge −2; two Weyl points with charge +1 (−1) paired with a Dirac point of charge −2 (+2); and two Weyl points with charge −2 paired with four Weyl points of charge +1. All of these configurations are consistent with the no-go theorem. Crystal symmetries constrain these quasiparticles to reside along high-symmetry points, lines, and planes in the Brillouin zone (BZ), giving rise to characteristic surface states that span the entire surface BZ and are readily identifiable. Furthermore, we demonstrate that the two enantiomeric structures of Pt3I8 carry opposite chiral topological charges. Our findings provide a valuable framework for investigating a wide range of topological phononic quasiparticles in chiral crystal systems.