Local inversion-symmetry breaking controls the boson peak in glasses and crystals

Article

关键词: DISORDERED SOLIDS;    MODES;    CRYSTALLIZATION;    EXCITATIONS;    SYSTEMS;    ORDER;   

DOI  :  10.1103/PhysRevB.93.094204

来源: SCIE

【 摘 要 】

It is well known that amorphous solids display a phonon spectrum where the Debye similar to omega(2) law at low frequency melds into an anomalous excess-mode peak (the boson peak) before entering a quasilocalized regime at higher frequencies dominated by scattering. The microscopic origin of the boson peak has remained elusive despite various attempts to put it in a clear connection with structural disorder at the atomic/molecular level. Using numerical calculations on model systems, we show that the microscopic origin of the boson peak is directly controlled by the local breaking of center-inversion symmetry. In particular, we find that both the boson peak and the nonaffine softening of the material display a strong correlation with a new order parameter describing the local inversion symmetry of the lattice. The standard bond-orientational order parameter, instead, is shown to be inadequate and cannot explain the boson peak in randomly-cut crystals with perfect bond-orientational order. Our results bring a unifying understanding of the boson peak anomaly for model glasses and defective crystals in terms of a universal local symmetry-breaking principle of the lattice.

【 授权许可】

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