Bending sound in graphene: origin and manifestation

TL;DR

This paper explains the origin of bending sound in graphene through a nonlinear interaction model, deriving an explicit expression for its speed and correlating it with experimental and simulation data.

Contribution

It introduces an original adiabatic approximation to describe bending sound in graphene and provides explicit formulas linking microscopic properties to observable sound characteristics.

Findings

Derived explicit expression for bending sound speed in graphene.

Confirmed the model's predictions with experimental and simulation data.

Identified the role of nonlinear strain interactions in bending mode dispersion.

Abstract

It is proved that the acoustic-type dispersion of bending mode in graphene is generated by the fluctuation interaction between in-plane and out-of-plane terms in the free energy arising with account of non-linear components in the graphene strain tensor. In doing so we use an original adiabatic approximation based on the alleged (confirmed a posteriori) significant difference of sound speeds for in-plane and bending modes. The explicit expression for the bending sound speed depending only on the graphene mass density, in-plane elastic constants and temperature is deduced as well as the characteristics of the microscopic corrugations of graphene. The obtained results are in good quantitative agreement with the data of real experiments and computer simulations.