Phonon spectrum and electron-phonon coupling in zigzag graphene nanoribbons

Abstract

In this paper, we report a first-principles study of the lattice dynamics of small graphene nanoribbon with zigzag edges. Our investigation is based on spin polarized density functional calculations (DFT). Nesting properties in the electronic band structure are very different for nanoribbons with unpolarized, ferromagnetic, and antiferromagnetic configurations. As a result, the phonon spectrum and nesting related softening in phonon frequencies differ in these cases. The unpolarized and ferromagnetic structures show nesting related phonon softening and considerable electron phonon linewidth, while for the antiferromagnetic structure, a band gap at the Fermi energy eliminates these effects. Saturating the nanoribbon edge with hydrogen has negligible effect on the phonon spectra for the magnetic structures while for the unpolarized configuration all structures without hydrogen are unstable due to soft phonon modes. The electron-phonon coupling coefficients have also been calculated and implications for Peierls transition and superconductivity are discussed.

Study of the superconducting phase in silicene under biaxial tensile strain

“…However, various theoretical calculations demonstrate that the phononmediated superconductivity does not occur in the intrinsic graphene, due to the weak electron-phonon coupling constant [10], [11], [12]. This fact follows the case of graphite, where the induction of the superconducting phase is possible only via the chemical process know as intercalation [13].…”

“…In this respect, the one-atom-thick two-dimensional form of carbon, known as graphene [6], attracted exceptional attention in recent years, when comparing to the other carbon allotropes [7], [8], [9]. However, various theoretical calculations demonstrate that the phononmediated superconductivity does not occur in the intrinsic graphene, due to the weak electron-phonon coupling constant [10], [11], [12]. This fact follows the case of graphite, where the induction of the superconducting phase is possible only via the chemical process know as intercalation [13].…”

Field-Induced Conformational Change in a Single-Molecule-Graphene–Nanoribbon Junction: Effect of Vibrational Energy Redistribution

“…(II) For excitations of the leads a different picture emerges. The electron–phonon coupling constant, as calculated by Zhang et al, was found to be strong (λ = 0.14) in periodic 2-ZGNR and 4-ZGNR. The phonon lifetimes of the associated bath modes, , are thus in the picosecond regime, much faster than the dynamics of the switching process reported here.…”

Electronic and thermal conduction properties of halogenated porous graphene nanoribbons

“…The scaling factor is the thermal conductance quantum κ 0 (T ) = exist for an infinite width, i.e. for the two-dimensional graphene sheet [38,39,40]. Furthermore, comparing the APG with the ZPG structures, one can see larger differences in κ ph (T ) for the two nanopore sizes in the former case, which may develop from an enhanced deformation of the APG structures.…”

“…Finite width nanoribbons are quasi one-dimensional systems and there are four acoustic phonon branches: the outof plane mode (ZA), the in-plane transverse mode (TA), the in-plane longitudinal (LA) and a torsion branch, which does not exist for an infinite width, i.e. for the two-dimensional graphene sheet [38,39,40]. Furthermore, comparing the APG with the ZPG structures, one can see larger differences in κ ph (T ) for the two nanopore sizes in the former case, which may develop from an enhanced deformation of the APG structures.…”