Double-Weyl phonons in transition-metal monosilicides

Abstract

Topological states of electrons and photons have attracted significant interest recently. Topological mechanical states also being actively explored, have been limited to macroscopic systems of kHz frequency. The discovery of topological phonons of atomic vibrations at THz frequency can provide a new venue for studying heat transfer, phonon scattering and electron-phonon interaction. Here, we employed ab initio calculations to identify a class of noncentrosymmetric materials of $M$Si ($M$=Fe,Co,Mn,Re,Ru) having double Weyl points in both their acoustic and optical phonon spectra. They exhibit novel topological points termed "spin-1 Weyl point" at the Brillouin zone~(BZ) center and "charge-2 Dirac point" at the zone corner. The corresponding gapless surface phonon dispersions are double helicoidal sheets whose isofrequency contours form a single non-contractible loop in the surface BZ. In addition, the global structure of the surface bands can be analytically expressed as double-periodic Weierstrass elliptic functions. Our prediction of topological bulk and surface phonons can be experimentally verified by neutron scattering and electron energy loss spectroscopy, opening brand new directions for topological phononics.

5 pages, 4 figures

References in corpus (12)

• Topological Photonics
• Topological Acoustics
• Phase transition between the quantum spin Hall and insulator phases in 3D: emergence of a topological gapless phase
• Observation of phononic helical edge states in a mechanical 'topological insulator'
• Observation of topological valley transport of sound in sonic crystals
• Topological Semimetals
• Computing topological invariants without inversion symmetry
• The phonon dispersion of graphite by inelastic x-ray scattering
• Multiple types of topological fermions in transition metal silicides
• Large Fermi Arcs in Unconventional Weyl Semimetal RhSi
• Topological Nature of the Phonon Hall Effect
• Nonlinear conduction via solitons in a topological mechanical insulator

Cited by in corpus (13)

• New classes of chiral topological nodes with non-contractible surface Fermi arcs in CoSi
• Phononic Helical Nodal Lines with $\mathcal{P}\mathcal{T}$ Protection in MoB${}_2$
• Twofold quadruple Weyl nodes in chiral cubic crystals
• Ideal Unconventional Weyl Point in a Chiral Photonic Metamaterial
• Quasiparticle Interference Evidence of the Topological Fermi Arc States in Chiral Fermionic Semimetal CoSi
• Chiral fermion reversal in chiral crystals
• Observation of multiple types of topological fermions in PdBiSe
• Single crystal growth and magnetoresistivity study of topological semimetal CoSi
• Spin-1 Weyl Point and Surface Arc State in a Chiral Phononic Crystal
• Topological band structure of surface acoustic waves on a periodically corrugated surface
• Topological excitations in quasi two-dimensional quantum magnets with weak interlayer interactions
• Extremely broadband topological surface states in a photonic topological metamaterials
• Discovery of ideal Weyl points with helicoid surface states