Lattice dynamics and electron-phonon interaction in (3,3) carbon nanotubes

TL;DR

This study uses ab-initio methods to analyze lattice dynamics and electron-phonon interactions in (3,3) carbon nanotubes, revealing a potential Peierls transition that could compete with superconductivity.

Contribution

It provides a comprehensive ab-initio analysis of electron-phonon coupling and lattice dynamics in (3,3) nanotubes, highlighting the possible Peierls transition.

Findings

Peierls transition temperature approx 40K

Peierls instability related to 2k_F nesting

Possible q=0 coupling causing phonon softening

Abstract

We present a detailed study of the lattice dynamics and electron-phonon coupling for a (3,3) carbon nanotube which belongs to the class of small diameter based nanotubes which have recently been claimed to be superconducting. We treat the electronic and phononic degrees of freedom completely by modern ab-initio methods without involving approximations beyond the local density approximation. Using density functional perturbation theory we find a mean-field Peierls transition temperature of approx 40K which is an order of magnitude larger than the calculated superconducting transition temperature. Thus in (3,3) tubes the Peierls transition might compete with superconductivity. The Peierls instability is related to the special 2k_F nesting feature of the Fermi surface. Due to the special topology of the (n,n) tubes also a q=0 coupling between the two bands crossing the Fermi energy at k_F is possible which leads to a phonon softening at the Gamma point.