Vibrational defects at the boson peak in 2D glasses

Abstract

The boson peak is a well known anomaly in glasses and amorphous materials which is related to the thermal properties of such materials. However, its origin is still a subject of active research. Recently, a theory based around string-like vibrational defects has been proposed and studied by various research groups. In this study, we will build off of previous works in this domain. Using computational tools such as molecular dynamics simulations to obtain model glassy systems, we first conduct a replication study to understand and verify the existence of these stringlets. Subsequently, we propose an alternate method of obtaining defects at the boson peak by disentangling quasi-localised modes from phonons at the boson peak. We then characterise the geometry and sizes of both types of defects, finding a them to be 2D in 2D glasses. We also attempt to reconcile the two methods of obtaining defects and suggest that they are both valid ways of identifying defects in amorphous solids. Finally, we relate the occurrence of these defects back to the boson peak, proposing that these defects regulate the size of the boson peak.