Theory of Superconducting Tc

Allen, Philip B.; Mitrović, B.

doi:10.1016/s0081-1947(08)60665-7

Cited by 341 publications

(348 citation statements)

References 132 publications

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“…Key points are that the pairing interaction will have a shape closely related to the real part of the susceptibility (but more strongly peaked in weak coupling), and that spin fluctuations are repulsive in a singlet channel. [101,102] Therefore the strongest interaction will be at (π,π) similar to the SDW, and will favor opposite sign order parameters on Fermi surface sections separated by this wavevector. Furthermore, the nesting related peak in χ(q) does not show strong fine structure on the scale of the small (electron or hole) Fermi surfaces nor is there strong k z dependence.…”

Section: Superconductivitymentioning

confidence: 99%

Electronic structure of Fe-based superconductors

Singh

2009

Physica C: Superconductivity

140

114

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Section: Superconductivitymentioning

confidence: 99%

Electronic structure of Fe-based superconductors

Singh

2009

Physica C: Superconductivity

140

114

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“…Within a spin fluctuation induced pairing approach analogous to that employed for Sr 2 RuO 4 the key ingredient is the integral over the Fermi surface of the kdependent susceptibility with a function of the assumed triplet symmetry, 8,9,17 i.e. in the simplest case, k·k ′ /kk ′ .…”

Section: 37mentioning

confidence: 99%

“…Although the exact pairing mechanism has not been established in these materials, it is presumed that spin fluctuations are involved, most probably the quantum critical fluctuations in the materials with co-existing ferromagnetism and superconductivity. [8][9][10][11][12][13][14] In Sr 2 RuO 4 , strong nesting related antiferromagnetic spin fluctuations are found in local density approximation (LDA) calculations and experiment. 15,16 In addition ferromagnetic fluctuations may also be present, and if so these would favor a triplet superconducting state.…”

mentioning

confidence: 99%

Quantum critical behavior and possible triplet superconductivity in electron-dopedCoO2sheets

Singh

2003

Phys. Rev. B

138

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Density functional calculations are used to investigate the doping dependence of the electronic structure and magnetic properties in hexagonal NaxCoO2. The electronic structure is found to be highly two dimensional, even without accounting for the structural changes associated with hydration. At the local spin density approximation level, a weak itinerant ferromagnetic state is predicted for all doping levels in the range x = 0.3 to x = 0.7, with competing but weaker itinerant antiferromagnetic solutions. The Fermi surface, as expected, consists of simple rounded hexagonal cylinders, with additional small pockets depending on the c lattice parameter. Comparison with experiment implies substantial magnetic quantum fluctuations. Based on the Fermi surface size and the ferromagnetic tendency of this material, it is speculated that a triplet superconducting state analogous to that in Sr2RuO4 may exist here.

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“…EPC quantities (i.e. Eliashberg α 2 F functions) are calculated in a standard way [24,25]. As the wires are metallic, a Gaussian smearing of width 0.001 Ha is used to improve the convergence with respect to the number of kpoints.…”

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confidence: 99%

Phonon band structure and electron-phonon interactions in metallic nanowires

Verstraete

Gonze

2006

Phys. Rev. B

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We present first-principles calculations of the phonon band structure and electron-phonon coupling in thin metallic nanowires. A full Brillouin zone analysis of the phonons is mandatory for the investigation of the nanowire structural stability: all the examined unstrained nanowires show instabilities whose wavevectors are located off the zone center. The unstable phonon modes are transverse, leading to a transition without a gap opening, in contrast with the usual Peierls distortion picture. Electron-phonon coupling yields orders-of-magnitude changes depending on the nanowire structure.PACS numbers: 71.15.Mb,73.21.Hb, Metallic nanowires consisting of a single chain of evenly spaced atoms (monowires) have long been a theorist's playground : they have inspired many model systems for electrons, phonons and their coupling. One dimensional (1D) metallic systems were shown to be unstable against longitudinal distortion (i.e. pairing) by Fröhlich[1] and Peierls [2] in the 50s. This is, however, a simplified situation, and more general distortions must be considered. Batra [3] showed that transverse distortions can give rise to a different type of transition, which does not open a gap around the Fermi level (a phenomenon he coined Gapless Peierls Transition -GPT). The consequences of electron-phonon coupling (EPC) in monowires have been the focus of recent studies, e.g.[4], in particular to determine the effect of phonons on conductivity. Peierls transitions have been seen in first-principles simulations of carbon nanotubes [5,6], and the issue of whether superconductivity can survive in 1D, despite Peierls transitions, is an open question. For both normal and superconductivity in 1D, understanding the interplay between structure, stability, and metallicity is essential for nanotechnological applications.Nanowires or nanotubes with diameters superior to a few nanometers are produced nowadays for many different atomic species. In the past decade, it has also become possible to experimentally create and examine wires comprising just a few or even one strand of atoms. The most impressive success has been with gold [7,8], but other metals have also been used in different experimental setups [9,10]. The potential applications of thin nanowires include integrating electronics on a molecular scale, improving scanning microscope tips, and increasing data storage densities if the wires are magnetic.In the first thin gold nanowires visualized with an electron microscope [7], a large distance was observed between neighboring atoms along the wire. This distance was explained using first-principles calculations[11] to be an average distance between second neighbors in a zigzag (ZZ) structure, obtained by a transverse period-doubling of the monowire. Structures with small angles ( 60 • ) between successive bonds have been found theoretically for many metals. Analogous ZZ structures, with an angle larger than 120 degrees, were proposed to be stable only for some metals (see e.g. Ref. 12).Although these striking examples point to the ...

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Theory of Superconducting Tc

Cited by 341 publications

References 132 publications

Electronic structure of Fe-based superconductors

Electronic structure of Fe-based superconductors

Quantum critical behavior and possible triplet superconductivity in electron-dopedCoO2sheets

Phonon band structure and electron-phonon interactions in metallic nanowires

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