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...
Using calculations from first principles, we investigate the lattice thermal conductivity of ideal monolayer and bilayer graphenes. Our result estimates that the intrinsic thermal conductivity of both materials is around 2200 W m −1 K −1 at 300 K, a value close to the one observed theoretically and experimentally in graphite along the basal plane. It also illustrates the expected T −1 dependence at higher temperatures. The little variation between monolayer and bilayer thermal conductivities suggests that the number of layers may not affect significantly the in-plane thermal properties of these systems. The intrinsic thermal conductivity also appears to be nearly isotropic for graphene.
This work presents the emergence of superconductivity in Ir - doped Weyl semimetal T$_d$ - MoTe$_{2}$ with broken inversion symmetry. Chiral anomaly induced planar Hall effect and anisotropic magneto-resistance confirm the topological semimetallic nature of Mo$_{1-x}$Ir$_{x}$Te$_{2}$. Observation of weak anisotropic, moderately coupled type-II superconductivity in T$_d$ -Mo$_{1-x}$Ir$_{x}$Te$_{2}$ makes it a promising candidate for topological superconductor.
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