Abstract
In this paper we study the optical conductivity and density of states (DOS) of doped gapped graphene beyond the Dirac cone approximation in the presence of electron-phonon (e-ph) interaction under strain, i.e., within the framework of a full π-band Holstein model, by using the Kubo linear response formalism that is established upon the retarded self-energy. A new peak in the optical conductivity for a large enough e-ph interaction strength is found which is associated to transitions between the midgap states and the Van Hove singularities of the main π-band. Optical conductivity decreases with strain and at large strains, the system has a zero optical conductivity at low energies due to optically inter-band excitations through the limit of zero doping. As a result, the Drude weight changes with e-ph interaction, temperature and strain. Consequently, DOS and optical conductivity remains stable with temperature at low e-ph coupling strengths.
Highlights
Graphene as a semimetal has a linear band structure near the Dirac points of the Brillouin zone, which this linearization of the band structure called the Dirac approximation and used to set up analytical expressions for several physical properties like electronics, optoelectronics, mechanics etc
In this paper we study the optical conductivity and density of states (DOS) of doped gapped graphene beyond the Dirac cone approximation in the presence of electronphonon (e-ph) interaction under strain, i.e., within the framework of a full π-band Holstein model, by using the Kubo linear response formalism that is established upon the retarded self-energy
Due to the atomic displacement within the plane, the longitudinal optical (LO) and transverse optical (TO) phonons which are degenerate at k = 0.10 Second, the lattice displacements due to the ripple structures, out-of-plane vibrations which are symmetric with respect to their close atoms and couple to the electronic densities
Summary
Scattered to a state with momentum k + q and energy εk + ωq via a absorption of a phonon with momentum q and energy ωq. The ab initio calculations[17] as well as experimental studies[18] have demonstrated that monolayer graphene can reversibly sustain elastic deformations as large as 20% In this regard, it has been proved that Raman spectroscopy can be used as a sensitive tool to stusy the strain as well as some strain-induced modifications of the electronic and optoelectronic properties of graphene.[19,20,21] The mechanical strain effects on graphene are important for applications such as flexible electronic devices. Our main goal in this manuscript is to study the effects of applied strain on the optical conductivity of gapped graphene which is subjected to a photon spectrum with frequency ω in the presence of phonons.
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