Anisotropic gap of superconducting<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>CaC</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math>: A first-principles density functional calculation

Sanna, Antonio; Profeta, G.; Floris, Andrea; Marini, Andrea; Gross, E. K. U.; Massidda, S.

doi:10.1103/physrevb.75.020511

Cited by 117 publications

(164 citation statements)

References 21 publications

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“…There are several reported FS, determined both experimentally 17,35 and theoretically 36,37 . These all exhibit the potential for nesting, namely that they have high symmetry, extended parallel portions of FS and significant density of states around the Fermi level.…”

Section: Discussionmentioning

confidence: 99%

Charge density waves in the graphene sheets of the superconductor CaC6

et al. 2011

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Graphitic systems have an electronic structure that can be readily manipulated through electrostatic or chemical doping, resulting in a rich variety of electronic ground states. Here we report the first observation and characterization of electronic stripes in the highly electrondoped graphitic superconductor, CaC 6 , by scanning tunnelling microscopy and spectroscopy. The stripes correspond to a charge density wave with a period three times that of the Ca superlattice. Although the positions of the Ca intercalants are modulated, no displacements of the carbon lattice are detected, indicating that the graphene sheets host the ideal charge density wave. This provides an exceptionally simple material-graphene-as a starting point for understanding the relation between stripes and superconductivity. Furthermore, our experiments suggest a strategy to search for superconductivity in graphene, namely in the vicinity of striped 'Wigner crystal' phases, where some of the electrons crystallize to form a superlattice.

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Section: Discussionmentioning

confidence: 99%

Charge density waves in the graphene sheets of the superconductor CaC6

et al. 2011

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“…It is then possible to restrict the Matsubara integration to a low energy ( a fraction of eV ) by a renormalization procedure µ → µ * introduced by Morel and Anderson 5,27,31 . µ * can be calculated within the random phase approximation 22,28,29 (RPA) and the resulting T c are usually in reasonable agreement with experiments 23,30 . However, usually µ * is adjusted to obtain the experimental T c .…”

Section: Methodsmentioning

confidence: 97%

Phononic self-energy effects and superconductivity in CaC6

et al. 2012

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We study the graphite intercalated compound CaC6 by means of Eliashberg theory. We perform an analysis of the electron-phonon coupling and define a minimal 6-band anisotropic structure, that leads to a Fermi surface dependance of the superconducting gap. A comparison of the superconducting gap structure obtained using the Eliashberg and the superconducting density functional theory is performed. We further report the anisotropic properties of the electronic spectral function, the polaronic quasi-particle branches and their interplay with Bogoljubov excitations.

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“…First-principles theoretical investigations on CaC 6 revealed that the superconducting critical temperature can be explained considering only the electron-phonon mechanism 47,48 , even if other pairing mechanisms were proposed (excitonic and plasmonic).…”

Section: B Cac6mentioning

confidence: 99%

Adiabatic and nonadiabatic phonon dispersion in a Wannier function approach

2010

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We develop a first-principles scheme to calculate adiabatic and non-adiabatic phonon frequencies in the full Brillouin zone. The method relies on the variational properties of a force-constants functional with respect to the first-order perturbation of the electronic charge density and on the localization of the deformation potential in the Wannier function basis. This allows for calculation of phonon dispersion curves free from convergence issues related to Brillouin zone sampling. In addition our approach justify the use of the static screened potential in the calculation of the phonon linewidth due to decay in electron-hole pairs. We apply the method to the calculation of the phonon dispersion and electron-phonon coupling in MgB2 and CaC6. In both compounds we demonstrate the occurrence of several Kohn anomalies, absent in previous calculations, that are manifest only after careful electron and phonon momentum integration. In MgB2, the presence of Kohn anomalies on the E2g branches improves the agreement with measured phonon spectra and affects the position of the main peak in the Eliashberg function. In CaC6 we show that the non-adiabatic effects on in-plane carbon vibrations are not localized at zone center but are sizable throughout the full Brillouin zone. Our method opens new perspectives in large-scale first-principles calculations of dynamical properties and electron-phonon interaction.

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Anisotropic gap of superconductingCaC6: A first-principles density functional calculation

Cited by 117 publications

References 21 publications

Charge density waves in the graphene sheets of the superconductor CaC6

Charge density waves in the graphene sheets of the superconductor CaC6

Phononic self-energy effects and superconductivity in CaC6

Adiabatic and nonadiabatic phonon dispersion in a Wannier function approach

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