A generalized two-band model for the superconductivity in MgB<sub>2</sub>

Konsin, P.; Sorkin, B.

doi:10.1088/0953-2048/17/12/019

Cited by 11 publications

(7 citation statements)

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“…Applying the standard techniques from single-band BCS theory allows evaluating various properties of the two-band system, such as the density of states, presented in figure 3, the temperature dependence of the energy gaps, and the transition temperature, which was shown to be higher than the values of each single-band [30]. Fitting two-band BCS theory to experimental specific heat data worked well for MgB 2 [3,[31][32][33], revealing that the jump at the transition temperature is smaller than in the single-band case. Furthermore, the effects on the superfluid density and the magnetic penetration depth were reported to agree with the experimental data quite well.…”

Section: Bcs Theory and Quasi-classical Equationsmentioning

confidence: 96%

A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties

Zehetmayer

2013

Supercond. Sci. Technol.

120

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Two-band superconductivity has become an important topic over the last ten years. Extensive experimental and theoretical studies started with MgB2 and are now focused on the iron-based and other new superconductors. In this review, I describe how important thermodynamic, reversible mixed-state, and other superconducting properties are changed by two-band and, for comparison, by other effects such as anisotropy in a single-band material or an energy gap structure different from the conventional s-wave symmetry. The work consists of three main parts, in which I review (i) theoretical models and what they predict for experimentally accessible properties in the two-band and other scenarios, (ii) experimental methods applied for investigating superconducting properties and the results obtained in potential two-band materials, and (iii) materials, for which two-or multi-band superconductivity has been suggested. It is shown that two-band effects appear in most of the analyzed properties and that they can be quite significant but usually fade away as interband interactions increase. Anisotropy often leads to similar modifications in single-band superconductors, which is why the distinction of two-band and anisotropy effects is usually difficult, particularly when the temperature dependence of the quantities is examined. In contrast, the field dependent effects are more often different and thus more often allow a reliable distinction between the models. CONTENTS

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Section: Bcs Theory and Quasi-classical Equationsmentioning

confidence: 96%

A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties

Zehetmayer

2013

Supercond. Sci. Technol.

120

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“…In this picture, superconductivity arises from coupling between intercalant s electrons and the graphite π electrons bands, with gaps of different magnitudes existing on different sheets of the Fermi surface. Such a scenario is plausible, as there are notable similarities between the GICs and MgB 2 [7,13], a known multi-gap superconductor. Indeed, some aspects of graphite intercalate superconductivity can be understood by this two-gap phenomenology, however there is little direct evidence to support this picture.…”

mentioning

confidence: 99%

“…Such a scenario is plausible, as there are notable similarities between the GICs and MgB 2 [7,13], a known multigap superconductor. Indeed, some aspects of graphite intercalate superconductivity can be understood by this two-gap phenomenology; however, there is little direct evidence to support this picture, and recent band structure calculations suggest this scenario is unlikely [14].…”

mentioning

confidence: 99%

Bulk Evidence for Single-Gaps-Wave Superconductivity in the Intercalated Graphite SuperconductorC6Yb

et al. 2007

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We report measurements of the in-plane electrical resistivity and thermal conductivity of the intercalated graphite superconductor C 6 Yb down to temperatures as low as T c =100. When a field is applied along the c axis, the residual electronic linear term 0 =T evolves in an exponential manner for H c1 < H < H c2 =2. This activated behavior is compelling evidence for an s-wave order parameter, and is a strong argument against the possible existence of multigap superconductivity. DOI: 10.1103/PhysRevLett.98.067003 PACS numbers: 74.70.Wz, 74.25.Fy, 74.25.Op Carbon is a remarkably versatile element -in its pure form it may exist as an electronic insulator, semiconductor, or semimetal depending on its bonding arrangement. When dopant atoms are introduced, superconductivity may be added to this list, observed in graphite [1,2], fullerenes [3], and even diamond [4]. Superconductivity in doped carbon was first discovered in the graphite intercalate compounds (GICs), materials composed of sheets of carbon separated by layers of intercalant atoms. The first of these compounds contained alkali atoms, and had modest transition temperatures of 0.13-0.5 K [1]. The recent discovery of T c 's two orders of magnitude higher than this in C 6 Yb [5] and C 6 Ca [5,6] has, however, refocused attention on this intriguing family of compounds.The effects of the intercalant atoms in the GICs are twofold: they dramatically change the electronic properties of the host graphite lattice by both increasing the separation of the carbon sheets, as well as contributing charge carriers. This causes the two-dimensional graphite bands to dip below the Fermi level. The graphite interlayer band, previously unoccupied, also crosses the new Fermi level, contributing three-dimensional, free-electron-like states located between the carbon sheets. This new interlayer band hybridizes strongly with the bands, and its occupation appears to be linked with the occurrence of superconductivity in the GICs [7].There are still several fundamental questions remaining about superconductivity in the GICs, especially in C 6 Yb and C 6 Ca, where little experimental data exist. The pairing mechanism is unresolved, with speculation ranging from a conventional route involving the intercalant phonons [8][9][10] to superconductivity via acoustic plasmons [7].Early theoretical studies motivated by the alkali-metal GICs [11,12] emphasized a two-gap model for the superconducting state, where gaps of different magnitudes exist on different sheets of the Fermi surface. Such a scenario is plausible, as there are notable similarities between the GICs and MgB 2 [7,13], a known multigap superconductor. Indeed, some aspects of graphite intercalate superconductivity can be understood by this two-gap phenomenology; however, there is little direct evidence to support this picture, and recent band structure calculations suggest this scenario is unlikely [14].A necessary starting point is to establish the superconducting order parameter, but in C 6 Yb, this task is complicated as th...

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“…28,29) We can estimate the formation energy using the one-dimensional Ginzburg-Landau theory phenomenologically without the magnetic field. 28,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] We describe component-1 and component-2 by the following pseudo-order parameters 1 ; 2 having their own phase, and amplitude, N : 62)…”

Section: I-solitonmentioning

confidence: 99%

Interpretation of Abnormal AC Loss Peak Based on Vortex-Molecule Model for a Multicomponent Cuprate Superconductor

Tanaka

Crisan

Shivagan

et al. 2007

jjap

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A generalized two-band model for the superconductivity in MgB₂

Cited by 11 publications

References 59 publications

A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties

A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties

Bulk Evidence for Single-Gaps-Wave Superconductivity in the Intercalated Graphite SuperconductorC6Yb

Interpretation of Abnormal AC Loss Peak Based on Vortex-Molecule Model for a Multicomponent Cuprate Superconductor

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A generalized two-band model for the superconductivity in MgB2

Cited by 11 publications

References 59 publications

A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties

A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties

Bulk Evidence for Single-Gaps-Wave Superconductivity in the Intercalated Graphite SuperconductorC6Yb

Interpretation of Abnormal AC Loss Peak Based on Vortex-Molecule Model for a Multicomponent Cuprate Superconductor

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A generalized two-band model for the superconductivity in MgB₂