Symmetry-Protected Ideal Type-II Weyl Phonons in CdTe

Area of Science:

• Condensed Matter Physics
• Quantum Field Theory
• Materials Science

Background:

• Topological quasiparticles, typically fermions in semimetals, are crucial for understanding quantum phenomena.
• Low-energy excitations in crystalline solids offer insights into elementary particle physics.

Purpose of the Study:

• To identify and characterize type-II Weyl phonons in realistic materials.
• To explore the role of symmetry in protecting nontrivial phonon properties.
• To investigate associated surface states and phenomena.

Main Methods:

• First-principles calculations
• Symmetry analysis
• Investigation of surface states on (001) and (111) surfaces

Main Results:

• Identification of ideal type-II Weyl phonons in zinc-blende cadmium telluride.
• Demonstration that these phonons originate from band inversion between acoustic and optical branches.
• Observation of robust type-II Weyl points along high-symmetry lines, protected by symmetry.
• Visualization of nontrivial phonon surface states and long phonon surface arcs connecting Weyl points of opposite chirality.

Conclusions:

• Cadmium telluride is a promising material for studying type-II Weyl phonons.
• Symmetry protection offers a route to realize nontrivial phonon properties in realistic materials.
• This research opens avenues for novel applications leveraging topological phonons.