Transverse intrinsic localized modes in monatomic chain and in graphene

TL;DR

This paper investigates transverse intrinsic localized modes in monatomic chains and graphene, revealing their potential for extremely long lifetimes due to weak anharmonic decay processes.

Contribution

It provides the first analytical and numerical analysis of transverse intrinsic localized modes in monatomic chains and graphene, highlighting their unique anharmonic properties and long lifetimes.

Findings

Transverse localized modes can exist with frequencies above phonon spectra.

These modes have extremely long lifetimes, potentially exceeding 10^10 periods.

Decay occurs only through weak anharmonic processes.

Abstract

In this paper an analytical and numerical study of anharmonic vibrations of monatomic chain and graphene in transverse (perpendicular) with respect to the chain/plane direction is presented. Due to the lack of odd anharmonicities and presence of hard quartic anharmonicity for displacements in this direction, there may exist localized anharmonic transverse modes with the frequencies above the spectrum of the corresponding phonons. Although these frequencies are in resonance with longitudinal (chain) or in-plane (graphene) phonons, the modes can decay only due to a weak anharmonic process. Therefore the lifetime of these vibrations may be very long. E.g. in the chain, according to our theoretical and numerical calculations it may exceed 10^10 periods. We call these vibrations as transverse intrinsic localized modes.