First-principles analysis of electron-phonon interactions in graphene

Abstract

The electron-phonon interaction in monolayer graphene is investigated using density-functional perturbation theory. The results indicate that the electron-phonon interaction strength is of comparable magnitude for all four in-plane phonon branches and must be considered simultaneously. Moreover, the calculated scattering rates suggest an acoustic-phonon contribution that is much weaker than previously thought, revealing an important role of optical phonons even at low energies. Accordingly it is predicted, in good agreement with a recent measurement, that the intrinsic mobility of graphene may be more than an order of magnitude larger than the already high values reported in suspended samples. DOI: 10.1103/PhysRevB.81.121412 PACS number͑s͒: 72.10.Di, 71.15.Mb, 72.80.Vp Graphene, a two-dimensional ͑2D͒ sheet of carbon atoms in a honeycomb lattice, continues to attract much attention due to its unique physical properties. Aside from a substantial academic interest resulting from the relativisticlike behavior of charge carriers, this material is considered very promising in device applications as it has an extremely high intrinsic mobility, even at room temperature. Although in realistic conditions ͑i.e., placed on a substrate͒ the mobility tends to decrease significantly due to the presence of additional scattering mechanisms at the interfaces, 1-3 much effort is currently being devoted to eliminate, or at least minimize, these effects which are detrimental to graphene transport characteristics. Therefore, it is crucial to develop an accurate knowledge of the electron-phonon scattering as it determines the ultimate limit of any electronic device performance. The strength of electron-phonon coupling is typically estimated using the deformation potential approximation ͑DPA͒; it has been applied for graphene by a number of authors. [4][5][6] When the corresponding deformation potential constant was estimated from the transport measurements, however, the results revealed a discrepancy that is too large to be ignored. 1,2,7 Moreover, a very recent observation of mobilities in excess of 10 7 cm 2 / V s at T Շ 50 K in the decoupled graphene 8 drastically departs from the conventionally accepted values, raising serious questions about the current understanding of the intrinsic transport characteristics of graphene. A detailed theoretical analysis of electron-phonon interaction beyond the DPA is clearly called for. In this work, we apply a first-principles approach based on density-functional theory ͑DFT͒ to calculate the electronphonon coupling strength in graphene. The obtained electron-scattering rates associated with all phonon modes are analyzed and the intrinsic resistivity and mobility of monolayer graphene are estimated as functions of temperature. The results clearly elucidate the role of different branches ͑particularly, the significance of optical phonons and intervalley scattering via acoustic phonons͒ as well as limitations of DPA. The obtained effective deformation potential constants suggest the possibil...

Unraveling the acoustic electron-phonon interaction in graphene

“…While the extracted value for the acoustic deformation potential is much smaller than experimental values, 5,[7][8][9]11 it is in better agreement with other ab initio results yielding 4.5 eV. 31 We also note that our findings for the value of the effective deformation potential are in stark contrast to those of Ref. 37, where the combined coupling to the TA and LA phonons is found to yield a deformation potential of 10-20 eV.…”

“…5,[7][8][9]11 On the other hand, theoretical studies of the acoustic electronphonon coupling yield much lower values on the order of 3.9-7.4 eV. [30][31][32] At the same time, different forms of the coupling matrix element are used in theoretical studies 20,32 making a direct comparison of the different values of the deformation potential difficult.…”

“…Even though the effect of acoustic phonon scattering on the transport properties of graphene has been studied widely in the literature, 20,30,31,[33][34][35][36][37] a complete study considering the full details of the coupling matrix element is still lacking. The purpose of the present study is to fill out this gap and provide a detailed analysis of the acoustic electron-phonon interaction in graphene and at the same time establish the intrinsic value of the effective deformation potential.…”

Highly anisotropic electronic transport properties of monolayer and bilayer phosphorene from first principles

“…22. For the phonon dynamics and the carrier-phonon interaction, each phonon is treated as a perturbation of the self-consistent potential within the linear response [i.e., density functional perturbation theory (DFPT)]. 20,23 The calculation of the potential change due to this perturbation gives the carrier-phonon interaction matrix element: 23,24 …”

Polaronic signatures and spectral properties of graphene antidot lattices

“…22,29 The coupling to acoustic phonons, on the other hand, is known to be rather weak in graphene and carbon nanotubes. 25,38 In our system, where acoustic phonons have even lower energies than in graphene and carbon nanotubes, this coupling is expected to be even weaker and can therefore be safely neglected. The momentum-space form of the e-ph-coupling Hamiltonian readŝ…”