Abstract
Within the model of stable random matrices possessing translational invariance, a two-dimensional (on a square lattice) disordered oscillatory system with random strongly fluctuating bonds is considered. By a numerical analysis of the dynamic structure factor S(q, ω), it is shown that vibrations with frequencies below the Ioffe-Regel frequency ωIR are ordinary phonons with a linear dispersion law ω(q) ∝ q and a reciprocal lifetime б ~ q3. Vibrations with frequencies above ωIR, although being delocalized, cannot be described by plane waves with a definite dispersion law ω(q). They are characterized by a diffusion structure factor with a reciprocal lifetime б ~ q2, which is typical of a diffusion process. In the literature, they are often referred to as diffusons. It is shown that, as in the three-dimensional model, the boson peak at the frequency ωb in the reduced density of vibrational states g(ω)/ω is on the order of the frequency ωIR. It is located in the transition region between phonons and diffusons and is proportional to the Young’s modulus of the lattice, ω b ≃E.
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Original Russian Text © D.A. Konyukh, Ya.M. Bel’tyukov, D.A. Parshin, 2018, published in Fizika Tverdogo Tela, 2018, Vol. 60, No. 2, pp. 369–375.
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Konyukh, D.A., Bel’tyukov, Y.M. & Parshin, D.A. Phonons, Diffusons, and the Boson Peak in Two-Dimensional Lattices with Random Bonds. Phys. Solid State 60, 376–381 (2018). https://doi.org/10.1134/S1063783418020142
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DOI: https://doi.org/10.1134/S1063783418020142