Scanning Tunneling Spectroscopy on the Novel Superconductor<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>CaC</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:math>

Bergeal, N.; Dubost, Vincent; Noat, Yves; Sacks, W.; Roditchev, Dimitri; Eméry, N.; Hérold, Claire; Marêché, J.F.; Lagrange, P.; Loupias, G.

doi:10.1103/physrevlett.97.077003

Cited by 73 publications

(87 citation statements)

References 19 publications

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“…These measurements are supported by Scanning Tunneling Spectroscopy [40], which shows that CaC6 has a single isotropic gap of 1.6 ± 0.2meV. In addition, heat capacity measurements by Kim et al [33] also confirm a fully gapped superconductor and the authors suggest that their data is consistent with an electron phonon coupling of λ = 0.70 ± 0.04.…”

Section: Empirical Aspects Of the Superconducting Ground-state In Gicssupporting

confidence: 73%

“…This technique allows both structural and electronic studies of materials. Scanning Tunneling spectroscopy (SPS) was first explored for CaC6 [40] and provided a verification of the superconducting energy gap consistent with that obtained by [39,42]. However, the work [40] was unable to obtain atomic-resolution images of the sample.…”

Section: Empirical Aspects Of the Superconducting Ground-state In Gicsmentioning

confidence: 99%

“…Scanning Tunneling spectroscopy (SPS) was first explored for CaC6 [40] and provided a verification of the superconducting energy gap consistent with that obtained by [39,42]. However, the work [40] was unable to obtain atomic-resolution images of the sample. Both atomic resolution of CaC6 and atomically resolved spectroscopy was reported in [55] for samples at T = 78 K. This work was of new significance since it proved for the first time the existence of the ground-state so-called charge density wave (CDW) in a GIC ( figure 1.7a).…”

Section: Empirical Aspects Of the Superconducting Ground-state In Gicsmentioning

confidence: 99%

“…and YbC6 could be related to a BCS pseudo-isotope effect, Hinks et al [40] measured the Ca isotope effect in CaC6. Hinks measured a large isotope effect with α = 0.50 ± 0.07 for Ca, suggesting that the superconductivity is due mainly to calcium phonon modes.…”

Section: Empirical Aspects Of the Superconducting Ground-state In Gicsmentioning

confidence: 99%

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Superconductivity in graphite intercalation compounds

Smith

Weller

Howard

et al. 2015

Physica C: Superconductivity and its Applications

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The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s [1,2]. This paper recontextualizes the field in light of the discovery of superconductivity in CaC6 and YbC6 in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how this relates to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.Corresponding author. Tel: +44 (0)7792954220 fax: +44 (0)20 7679 7145 e-mail address: mark.ellerby@ucl.ac.uk (Mark Ellerby).

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Section: Empirical Aspects Of the Superconducting Ground-state In Gicssupporting

confidence: 73%

Section: Empirical Aspects Of the Superconducting Ground-state In Gicsmentioning

confidence: 99%

Section: Empirical Aspects Of the Superconducting Ground-state In Gicsmentioning

confidence: 99%

Section: Empirical Aspects Of the Superconducting Ground-state In Gicsmentioning

confidence: 99%

See 2 more Smart Citations

Superconductivity in graphite intercalation compounds

Smith

Weller

Howard

et al. 2015

Physica C: Superconductivity and its Applications

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“…Despite its much higher T c , CaC 6 can also be described as a classical BCS superconductor with an isotropic gap. The zero temperature gap value is ∼1.7 meV [15] [16]. The upper critical field, H c2 , shows a remarkable anisotropy with the zero temperature value changing between ∼0.4 T and ∼1.9 T, depending on the external magnetic field direction [17].…”

Section: Introductionmentioning

confidence: 95%

Electron spin dynamics of the superconductorCaC6probed by ESR

et al. 2008

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Conduction Electron Spin Resonance (CESR) was measured on a thick slab of CaC6 in the normal and superconducting state. Non-linear microwave absorption measurements in the superconducting state describe CaC6 as an anisotropic BCS superconductor. CESR data in the normal state characterize CaC6 as a three-dimensional (3D) metal. The analysis suggests that the scattering of conduction electrons is dominated by impurities and supports the description of superconductivity in the dirty limit. A surprising increase of the CESR intensity below Tc can not be explained by the theoretically predicted change in spin susceptibility. It is interpreted as a vortex enhanced increase of the effective skin depth. The study of the spin dynamics in the superconducting state and the discovery of the vortex enhanced increase of the skin depth poses a challenge to theory to provide a comprehensive description of the observed phenomena.

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Superconductivity of K‐Intercalated Epitaxial Bilayer Graphene

Huempfner

Otto

Forker

et al. 2023

Adv Materials Inter

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In particular, graphene-based materials attracted considerable scientific interest due to the recent discovery of superconductivity in twisted bilayer graphene. [3][4][5] Superconductivity has also been observed in layered, graphene-based systems upon chemical doping via metal intercalation, with transition temperatures up to 11.5 K for calcium-intercalated bulk graphite. [6,7] However, for metal-intercalated, graphenebased systems the reported critical temperatures strongly depend on i) the choice of the atomic species used for metal intercalation and ii) the number of adjacent graphene layers. [6][7][8][9][10][11][12][13] Superconductivity in metal-intercalated bulk graphite is believed to originate from electron-phonon coupling (EPC) of electrons located in the energetically shifted π* bands of graphene and parabolic interlayer states, which are occupied upon chemical doping. There, the electrons are coupled to vibrations of the graphene lattice and the metal intercalants, where low-energy modes are particularly important. [14][15][16][17][18][19][20] Accordingly, the deviating properties observed for finite numbers of graphene layers are attributed to effects of low dimensionality that might alter the EPC strength and the interlayer state. [11,13,21] However, the mechanisms leading to superconductivity in graphene thin-films are not entirely understood yet. Both the existence of multiple energy gaps that originate from pairing on different Fermi surfaces [22] and various pairing symmetries [23][24][25][26][27] have been predicted for monolayer and few-layer graphene.Detailed structural and electronic properties of our K-intercalated epitaxial bilayer graphene (BLG) on SiC(0001) are characterized in a separate publication. [28] The K atoms form a highly ordered (2 × 2) registry with respect to the graphene lattice below the topmost graphene layer, see Figure 1. However, potassium also intercalates between the SiC substrate and the buffer layer, which causes electronic decoupling of the latter from the underlying substrate. Consequently, epitaxial monolayer graphene (MLG) undergoes a transition to K-intercalated epitaxial BLG as sketched in Figure 1c, where the lateral structure of the lower-lying potassium atoms remains unknown. This configuration promotes a rigid shift of the energetically non-separated Dirac bands of both layers to higher binding energies, accompanied by a filling of two interlayer bands, which were determined on both local and area-averaged scales via Fourier-transform scanning tunneling Graphene-based materials are among the most promising candidates for studying superconductivity arising from reduced dimensionality. Apart from doping by twisted stacking, superconductivity can also be achieved by metalintercalation of stacked graphene sheets, where the properties depend on the choice of the metal atoms and the number of graphene layers. Many different and even unconventional pairing mechanisms and symmetries are predicted in the literature for graphene monolayers and few-layers. However, t...

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Scanning Tunneling Spectroscopy on the Novel SuperconductorCaC6

Cited by 73 publications

References 19 publications

Superconductivity in graphite intercalation compounds

Superconductivity in graphite intercalation compounds

Electron spin dynamics of the superconductorCaC6probed by ESR

Superconductivity of K‐Intercalated Epitaxial Bilayer Graphene

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