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】
Free