Intra- and Interlayer Electron-Phonon Interactions in 12/12C and 12/13C BiLayer Graphene

Abstract

This review focuses on intra-and interlayer (IL) electron-phonon interactions and phonon self-energy renormalizations in twisted and AB-stacked bilayer graphene (2LG) composed either only of 12 C or a mixing of 12 C and 13 C isotopes. A simple way to imagine a 2LG is by placing one monolayer graphene (1LG) on top of another 1LG. The orientation of one of the layers with relation to the other may originate a twisted 2LG system (known as turbostratic) as well as a AB-stacked system, also known as Bernal stacking. By rotating the layers of a 2LG one can departure from a fully misoriented system to achieve the AB-stacked configuration and their IL interactions can be dramatically different being close to zero in a fully misoriented system and maximum in an AB-stacked system. Interlayer interactions are expected to slightly perturb the intralayer phonons and they also govern the low-energy electronic and vibrational properties, which are of primary importance to phenomena such as transport, infrared (IR) optics and telecommunication bands in the IR range. Therefore, a comprehensive discussion combining intra-and interlayer phenomena is necessary and addressed throughout the text.

A Review of Double-Walled and Triple-Walled Carbon Nanotube Synthesis and Applications

“…The (n, m) index will, therefore, also define whether a carbon nanotube is metallic or semiconducting. Additionally, due to the carbon nanotube one-dimensional character, both the electronic and the vibrational structures of CNTs present Van Hove singularities (VHS), and these VHS enhance many phenomena involving electrons, phonons and their mutual interactions, which are often called many-body interactions [2,4,5,[7][8][9][10]. These VHS have a high density of states, and they result from the quantum confinement observed in the circumferential direction of the nanotubes [2,4,5,7,8].…”

Probing the interaction of noble gases with pristine and nitrogen-doped graphene through Raman spectroscopy

“…Another way to explain our observations would be to correlate them to doping processes during the adlayer adsorption. However, we discard this possibility for two reasons: (1) the adlayers are formed with noble gases, which are neutral and very stable so the likelihood of having them ionized under the experimental conditions presented here is low, and (2) as well stablished in the literature, the doping mechanism in graphene layers changes frequencies, linewidths and intensities of the G-and 2Dbands [39][40][41][42][43][44][45][46][47] . Most of the times, doping causes a frequency blueshift, a linewidth narrowing and an intensity decrease for the G-band, regardless of if the doping is a p-or n-type doping, while for the 2D-band the frequency may blueshift (redshift), the linewidth may narrow (broaden) and the intensity may decrease (increase) if the sample is p-doping (n-doping).…”

“…Most of the times, doping causes a frequency blueshift, a linewidth narrowing and an intensity decrease for the G-band, regardless of if the doping is a p-or n-type doping, while for the 2D-band the frequency may blueshift (redshift), the linewidth may narrow (broaden) and the intensity may decrease (increase) if the sample is p-doping (n-doping). All the 2D-band features will substantially change even under a low doping level [39][40][41][42][43][44][45][46][47] . Based on these facts, it is possible to conclude that the analysis of films are most likely completely pinned to pristine graphene 20 .…”

“…8(d)), while the G-band frequency downshifts from 1586 to 1581.2 cm -1 . To understand these downshifts, we must recall about the main mechanisms that contribute to frequency downshifts: (1) phonon anharmonicities and electron-phonon coupling changes due to increases in temperature 39,[67][68][69][70][71][72] , (2) Quasi-particles renormalizations and charge transfer between carbon and adsorbents [40][41][42][43][44][45][46][47] , and (3) release of biaxial compressive strain and(or) uniaxial strains 35,36,52 .…”

Topological insulators in ordered double transition metals M$'_2$M$"$C$_2$ (M$'$= Mo, W; M$"$= Ti, Zr, Hf) MXenes

“…2, we find that all phonon modes are positive, indicating that the predicted structures are dynamically stable. The highest phonon frequency in M ′ 2 M ′′ C 2 O 2 MXenes is around 780 cm −1 , which is higher than that for MoS 2 475 cm −1 [82], but lower than that for graphene 1600 cm −1 [83]. This indicates the M ′ 2 M ′′ C 2 O 2 MXenes have higher (lower) stability than MoS 2 (graphene).…”