Physics of the Solid State
Volumes and Issues
Indirect interaction of the carbon atoms as the origin of the epitaxial graphene frequencies shift
Davydov S.Ju.1
1Ioffe Institute, St. Petersburg, Russia
Email: Sergei_Davydov@mail.ru

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To determine the effect of the substrate on the optical frequency ωLO(Γ) of free-standing graphene, the problem of the adsorbed on a solid substrate dimer, consisting of two carbon atoms bound by direct (kinetic) t and indirect tind (through the state of the substrate) exchanges, is considered. It is shown that in the case of a semiconductor substrate, the resulting interaction is t+|tind|, which leads to a frequency ωLO(Γ) shift by ΔωLO(Γ)>0 (red shift of the Raman G-peak) and a relative shift δLO(Γ)=ΔωLO(Γ)/ ωLO(Γ)~|tind|/t. The numerical estimates of δLO(Γ) made for the 6H-SiC substrate are in good agreement with the experimental data. In the case of a transition metal substrate, it is shown that for metals with large effective masses of d-electrons (elements of the end of the 3d-series), a situation ΔLO(Γ)<0 is possible (blue shift), which actually takes place for graphene formed on Ni(111). Here, however, the theoretical estimates of |δLO(Γ)| are underestimated. Keywords: direct and indirect exchange, longitude optical frequency, SiC and d-metal substrates.
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Ioffe Institute

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Director: Sergei V. Ivanov

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