Reduction of Fermi velocity in folded graphene observed by resonance Raman spectroscopy

TL;DR

This study uses resonance Raman spectroscopy to observe a reduction in Fermi velocity in folded graphene sheets with non-AB stacking, revealing how stacking order affects electronic properties.

Contribution

It demonstrates that folded graphene with various stacking configurations exhibits a measurable decrease in Fermi velocity, expanding understanding of electronic structure modifications.

Findings

Blue shift of 2D band indicates reduced Fermi velocity (~5.6%)

Different stacking and twist angles cause variable Fermi velocity reductions

Raman spectroscopy effectively probes electronic structure changes in folded graphene

Abstract

The 1+1 layer folded graphene sheets that deviate from AB stacking are successfully fabricated and their electronic structures are investigated by Raman spectroscopy. Significant blue shift of the 2D band of folded graphene compared to that of single layer graphene (SLG) is observed. This is attributed to SLG-like electronic structure of folded graphene but with slowing down of Fermi velocity (as much as ~5.6%). Different amount of blue shift of 2D band is observed for different folded graphenes, which may correspond to the different twist angle and/or separation between the two layers, resulting in different Fermi velocity of folded graphenes. Electronic structure of 1+1 folded graphene samples with different stacking order (twist and separation between the two layers, and in-plane shift of the two layers) can be investigated by Raman spectroscopy.