Boson peak: Damped phonon in solids

Abstract

The boson peak has long been considered an exclusive fingerprint of structural glasses, attributed to the disordered structure nature of glass. However, numerous studies also revealed the existence of boson peaks in many crystalline materials. The paradox is an unsolved knot in condensed matter physics. Here, we systematically explore the boson peaks in various disordered materials via a low-temperature specific heat perspective. A linear relationship between the boson peak temperature and the transverse sound velocity is well established, which indicates the phonon nature of the boson peak. Further analysis reveals that the boson peak is a ubiquitous hallmark of all solids that originates from the transverse mode damping, and glasses with disordered structures could enhance the phonon damping and result in the distinct boson peak phenomenon. The results have benefits for a better understanding of the structural origins of boson peaks.