Superfluid density of bulk CaC6

Lamura, G.; Aurino, Mario; Cifariello, G.; Gennaro, Emiliano Di; Andreone, A.; Eméry, N.; Hérold, Claire; Marêché, J.F.; Lagrange, P.

doi:10.1016/j.physc.2007.03.387

Cited by 8 publications

(7 citation statements)

References 11 publications

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“…Experimental data seem to confirm that the pairing in CaC 6 and YbC 6 is indeed due to the electron-phonon interaction, but several open questions remain. From the exponential behavior of the penetration depth in CaC 6 Lamura et al 12 deduced an isotropic gap of magnitude ∆(0)=1.79± 0.08 meV. A similar isotropic gap (∆(0)=1.6± 0.2 meV) has been measured by scanning tunneling spectroscopy 13 .…”

Section: Introductionmentioning

confidence: 62%

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Possibility of superconductivity in graphite intercalated with alkaline earths investigated with density functional theory

Calandra

Mauri

2006

Phys. Rev. B

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Using density functional theory we investigate the occurrence of superconductivity in AC6 with A=Mg,Ca,Sr,Ba. We predict that at zero pressure, Ba and Sr should be superconducting with critical temperatures (Tc) 0.2 K and 3.0 K, respectively. We study the pressure dependence of Tc assuming the same symmetry for the crystal structures at zero and finite pressures. We find that the SrC6 and BaC6 critical temperatures should be substantially enhanced by pressure. On the contrary, for CaC6 we find that in the 0 to 5 GPa region, Tc weakly increases with pressure. The increase is much smaller than what shown in several recent experiments. Thus we suggest that in CaC6 a continous phase transformation, such as an increase in staging, occurs at finite pressure. Finally we argue that, although MgC6 is unstable, the synthesis of intercalated systems of the kind MgxCa1−xCy could lead to higher critical temperatures.

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Section: Introductionmentioning

confidence: 62%

“…From the exponential behavior of the penetration depth in CaC 6 Lamura et al 12 deduced an isotropic gap of magnitude ∆(0)=1.79± 0.08 meV. A similar isotropic gap (∆(0)=1.6± 0.2 meV) has been measured by scanning tunneling spectroscopy 13 .…”

Section: Introductionmentioning

confidence: 62%

Possibility of superconductivity in graphite intercalated with alkaline earths investigated with density functional theory

Calandra

Mauri

2006

Phys. Rev. B

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“…Layers thick compared to the penetration depth would presum-10 A free-standing superconducting layer (or a layer surrounded by insulators) with thickness small compared to the magnetic penetration depth λ can have an enormous superheating field (since it can remain superconducting without paying most of the cost of expelling the flux). In the accelerator community, there is widespread focus on raising this 'H c1 ' for the superconducting film [74,75] -defined, somewhat unphysically [76] as the minimum field needed for a vortex to be stable parallel to and inside the film. But such an in-film stable vortex configuration demands magnetic flux on both sides of the film.…”

Section: Laminates and Vortex Penetrationmentioning

confidence: 99%

Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: stability theory, disorder, and laminates

Liarte

Posen

Transtrum

et al. 2017

Supercond. Sci. Technol.

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Theoretical limits to the performance of superconductors in high magnetic fields parallel to their surfaces are of key relevance to current and future accelerating cavities, especially those made of new higher-Tc materials such as Nb3Sn, NbN, and MgB2. Indeed, beyond the so-called superheating field H sh , flux will spontaneously penetrate even a perfect superconducting surface and ruin the performance. We present intuitive arguments and simple estimates for H sh , and combine them with our previous rigorous calculations, which we summarize. We briefly discuss experimental measurements of the superheating field, comparing to our estimates. We explore the effects of materials anisotropy and the danger of disorder in nucleating vortex entry. Will we need to control surface orientation in the layered compound MgB2? Can we estimate theoretically whether dirt and defects make these new materials fundamentally more challenging to optimize than niobium?Finally, we discuss and analyze recent proposals to use thin superconducting layers or laminates to enhance the performance of superconducting cavities. Flux entering a laminate can lead to so-called pancake vortices; we consider the physics of the dislocation motion and potential re-annihilation or stabilization of these vortices after their entry.

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“…The superconducting mechanism of GICs has been more deeply debated based on experimental and theoretical studies on superconducting CaC 6 . The resulting in-plane magnetic penetration depth suggests an isotropic s-wave pairing, and the value of ( )/ ∆ k T 2 0 B c (=3.6 ± 0.2) indicates a weakly coupled superconductor [45], where 2Δ(0) and k B are the superconducting gap and Boltzmann constant, respectively. Specific heat measurements showed an anomalous characteristic of the superconducting transition just at T c , which is an indication of bulk superconductivity [46].…”

Section: Superconducting Mechanism and Electronic Structure Of Gic Su...mentioning

confidence: 99%

Recent progress on carbon-based superconductors

Kubozono

Eguchi

Goto

et al. 2016

J. Phys.: Condens. Matter

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This article reviews new superconducting phases of carbon-based materials. During the past decade, new carbon-based superconductors have been extensively developed through the use of intercalation chemistry, electrostatic carrier doping, and surface-proving techniques. The superconducting transition temperature T c of these materials has been rapidly elevated, and the variety of superconductors has been increased. This review fully introduces graphite, graphene, and hydrocarbon superconductors and future perspectives of high-T c superconductors based on these materials, including present problems. Carbon-based superconductors show various types of interesting behavior, such as a positive pressure dependence of T c. At present, experimental information on superconductors is still insufficient, and theoretical treatment is also incomplete. In particular, experimental results are still lacking for graphene and hydrocarbon superconductors. Therefore, it is very important to review experimental results in detail and introduce theoretical approaches, for the sake of advances in condensed matter physics. Furthermore, the recent experimental results on hydrocarbon superconductors obtained by our group are also included in this article. Consequently, this review article may provide a hint to designing new carbon-based superconductors exhibiting higher T c and interesting physical features.

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Superfluid density of bulk CaC6

Cited by 8 publications

References 11 publications

Possibility of superconductivity in graphite intercalated with alkaline earths investigated with density functional theory

Possibility of superconductivity in graphite intercalated with alkaline earths investigated with density functional theory

Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: stability theory, disorder, and laminates

Recent progress on carbon-based superconductors

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