Features of the propagation of phonons in graphene nanostructures. Fast high-frequency phonons in a quasi-flexural mode
S. B. Feodosyev, I. A. Gospodarev, V. A. Sirenko, E. S. Syrkin, and I. S. Bondar
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine Kharkiv 61103, Ukrain
Received December 24, 2021, published online June 20, 2022
The character of propagation in graphene nanostructures of quasi-flexural phonons, whose dispersion law differs from the sound one, is analyzed. Based on the calculation of the frequency dependences of the group velocities and the values of the path of quasiparticles for one period of oscillation, the frequency intervals are established at which: i) phonons propagate freely along all directions of reciprocal space — the propagon zone; ii) phonon propagation along some directions is impossible — diffuse zone; iii) phonons are localized at the nodes of the honeycomb lattice — the locon zone. A comparison is made with a similar classification of phonons in a three-dimensional crystal of cubic symmetry.
Key words: phonon, graphene nanostructure, vibrational characteristics.