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Using the {\it ab initio} anisotropic Eliashberg theory including Coulomb interactions, we investigate the electron-phonon interaction and the pairing mechanism in the recently-reported superconducting Ca-intercalated bilayer graphene. We…

Superconductivity · Physics 2016-01-25 E. R. Margine , Henry Lambert , Feliciano Giustino

The superconductor YB6 has the second highest critical temperature Tc among the boride family MBn. We report measurements of the specific heat, resistivity, magnetic susceptibility and thermal expansion from 2 to 300 K, using a single…

Superconductivity · Physics 2009-11-11 R. Lortz , Y. Wang , U. Tutsch , S. Abe , C. Meingast , P. Popovich , W. Knafo , N. Shitsevalova , Yu. B. Paderno , A. Junod

We report measurements of the in-plane electrical resistivity $\rho$ and the thermal conductivity $\kappa$ of the intercalated graphite superconductor C$_6$Yb to temperatures as low as $T_c$/100. When a field is applied along the c-axis,…

Superconductivity in graphite intercalated compounds has been studied for more than 40 years and it is still not fully understood, despite the recent progress and the discovery of relatively high Tc superconductivity in CaC6 and YbC6.…

Superconductivity · Physics 2009-04-14 T. Valla , J. Camacho , Z-H. Pan , A. V. Fedorov , A. C. Walters , C. A. Howard , M. Ellerby

Terahertz reflectance spectra of the Ca-intercalated graphite CaC6 reveal a superconducting gap below 11K. The gap signature lacks a sharp onset to full reflectivity at 2Delta, but rather shows a distribution of gap values consistent with…

Superconductivity · Physics 2009-11-13 U. Nagel , D. Huvonen , E. Joon , J. S. Kim , R. K. Kremer , T. Room

We report anisotropy of the upper critical field (Bc2) of an intercalated graphite superconductor YbC6 (Tc = 6.5 K) determined from angular dependent magnetoresistance measurements. Though the perpendicular coherence length is much longer…

Superconductivity · Physics 2008-11-19 N. F. Kawai , Hiroshi Fukuyama

Point-contact tunneling on CaC$_6$ crystals reproducibly reveals superconducting gaps, $\Delta$, of 2.3$\pm$0.2 meV which are $\sim$~40% larger than earlier reports. That puts CaC$_6$ into the class of very strong-coupled superconductors…

Superconductivity · Physics 2008-03-05 C. Kurter , L. Ozyuzer , Daniel Mazur , J. F. Zasadzinski , D. Rosenmann , H. Claus , D. G. Hinks , K. E. Gray

We have performed photoemission studies of the electronic structure in LiC$_6$ and KC$_8$, a non-superconducting and a superconducting graphite intercalation compound, respectively. We have found that the charge transfer from the…

Superconductivity · Physics 2011-05-20 Z. -H. Pan , J. Camacho , M. H. Upton , A. V. Fedorov , C. A. Howard , M. Ellerby , T. Valla

Although not an intrinsic superconductor, it has been long--known that, when intercalated with certain dopants, graphite is capable of exhibiting superconductivity. Of the family of graphite--based materials which are known to superconduct,…

Superconductivity · Physics 2016-08-16 Gabor Csányi , P. B. Littlewood , A. H. Nevidomskyy , Chris J. Pickard , B. D. Simons

We report experimental results indicating possible high-temperature superconductivity in graphite intercalation compounds synthesized with lithium-based alloys. Temperature-dependent measurements of magnetization, trapped magnetic flux, and…

We present a theoretical investigation on electron-phonon superconductivity of honeycomb MX$_2$ layered structures. Where X is one element of the group-IV (C, Si or Ge) and M an alkali or an alkaline-earth metal. Among the studied…

Superconductivity · Physics 2015-06-23 José A. Flores-Livas , Antonio Sanna

Light-matter interactions have generated considerable interest as a means to manipulate material properties. Light-induced superconductivity has been demonstrated using pulsed lasers. An attractive alternative possibility is to exploit…

We have obtained bulk samples of the graphite intercalation compound, CaC6, by a novel method of synthesis from highly oriented pyrolytic graphite. The crystal structure has been completely determined showing that it is the only member of…

Materials Science · Physics 2009-11-11 N. Emery , C. Herold , M. d Astuto , V. Garcia , Ch. Bellin , J. F. Mareche , P. Lagrange , G. Loupias

We present the results of a neutron scattering study of the high energy phonons in the superconducting graphite intercalation compound CaC$_6$. The study was designed to address hitherto unexplored aspects of the lattice dynamics in…

Search for new high-temperature superconductors and insight into their superconducting mechanism are of fundamental importance in condensed matter physics. The discovery of near-room temperature superconductivity at more than a million…

A recent ab initio investigation of Na-C binary compounds under moderate pressures has uncovered a possible stable NaC$_4$ superconductor with an estimated critical temperature up to 41K. We revisit this promising binary system by…

We investigate the dispersion and temperature dependence of a number of phonons in the recently discovered superconductor CaC6 utilizing inelastic x-ray scattering. Four [00L] and two ab-plane phonon modes are observed, and measured at…

Graphite intercalation compounds (GICs) have long been recognized as promising candidates for high-temperature superconductivity by intercalation or charge doping, yet experimental progress has stalled with transition temperatures (Tc)…

Lortz et al. [Phys. Rev. B 73, 024512 (2006)] have utilized specific heat and resistivity measurements as "thermal spectroscopies" to deconvolve the spectrum of the electron-phonon interaction in YB$_6$ assuming a major role of the low…

Superconductivity · Physics 2013-04-01 P. Szabo , J. Girovsky , Z. Pribulova , J. Kacmarcik , T. Mori , P. Samuely

We review the characteristics of some carbon based novel superconductors which emerged in the past two decades since the discovery of superconductivity in the high-T_c oxocuprates. In particular, we summarize the properties of ternary…

Superconductivity · Physics 2007-05-23 Reinhard K. Kremer , Jun Sung Kim , Arndt Simon