Superconductivity in Transition-Metal Alloys

Vonsovsky, Serghey V.; Izyumov, Yu. A.; Kurmaev, E.Z.

doi:10.1007/978-3-642-61819-2_5

Cited by 55 publications

(104 citation statements)

References 69 publications

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“…We can use K c (ω) as a kernel in the linearized gap equation (Cf. Appendix B) determining T c which is a reasonable generalization of a Coulomb kernel used in the theory of ordered superconductors 151 . In momentum representation:…”

Section: Coulomb Kernelmentioning

confidence: 99%

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Superconductivity and localization

1997

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We present a review of theoretical and experimental works on the problem of mutual interplay of Anderson localization and superconductivity in strongly disordered systems. Superconductivity exists close to the metalinsulator transition in some disordered systems such as amorphous metals, superconducting compounds disordered by fast neutron irradiation etc. Hightemperature superconductors are especially interesting from this point of view. Only bulk systems are considered in this review. The superconductor-insulator transition in purely two-dimensional disordered systems is not discussed.We start with brief discussion of modern aspects of localization theory including the basic concept of scaling, self-consistent theory and interaction effects. After that we analyze disorder effects on Cooper pairing and superconducting transition temperature as well as Ginzburg-Landau equations for superconductors which are close to the Anderson transition. A necessary generalization of usual theory of "dirty" superconductors is formulated which allows to analyze anomalies of the main superconducting properties close to disorder-induced metal-insulator transition. Under very rigid conditions superconductivity may persist even in the localized phase (Anderson insulator).Strong disordering leads to considerable reduction of superconducting transition temperature T c and to important anomalies in the behavior of the upper critical field H c2 . Fluctuation effects are also discussed. In the vicinity of Anderson transition inhomogeneous superconductivity appears due to statistical fluctuations of the local density of states.We briefly discuss a number of experiments demonstrating superconductivity close to the Anderson transition both in traditional and high-T c superconductors. In traditional systems superconductivity is in most cases destroyed before metal-insulator transition. In case of high-T c superconductors a number of anomalies show that superconductivity is apparently conserved in the localized phase before it is suppressed by strong enough disorder. The concept of electron localization 1 is basic for the understanding of electron properties of disordered systems 2,3 . In recent years a number of review papers had appeared, extensively discussing this problem [4][5][6][7] . According to this concept introduction of sufficiently strong disorder into a metallic system leads to spatial localization of electronic states near the Fermi level and thus to a transition to dielectric state (Anderson transition). After this transition dc conductivity (at zero temperature, T = 0) vanishes, despite the finite value of electronic density of states at the Fermi level (at least in one-electron approximation).At the same time it is well-known that even the smallest attraction of electrons close to the Fermi level leads to formation of Cooper pairs and the system becomes superconducting at sufficiently low temperatures 8,9 . It is known that the introduction of disorder which does not break the time-reversal invariance (normal, nonm...

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Section: Coulomb Kernelmentioning

confidence: 99%

“…Superconducting transition temperature T c is determined by the linearized gap equation 151 which in the weak coupling approximation can be written as (Cf. Appendix B) 156,157 :…”

Section: Metallic Regionmentioning

confidence: 99%

Superconductivity and localization

1997

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“…The developed theories do not explain the possibility of creating high-temperature superconducting materials (HTSC) which are studied mostly empirically, by complication of their composition and structure and identifying correlations between the obtained properties, occurring physical and chemical processes and external thermal, electrical, magnetic and other influences. Fundamental and practical physical and chemical problems and results of these studies are published in numerous original articles as well as in various summary reviews and monographs [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] where other details and additional references can be found.…”

Section: Introductionmentioning

confidence: 99%

High-temperature superconductivity: From macro- to nanoscale structures

Коваленко¹

2016

Nanosystems: Phys. Chem. Math.

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The analysis of achievements, problems and prospects of high-temperature superconductivity (HTSC) in the macro-and nanostructured materials has been given. The main experimental results and theoretical models describing the physical mechanisms of the superconductivity appearance at phenomenological and microscopic levels, including change in the energy spectrum of atoms in these materials with the advent of the 'superconducting' gap at temperatures below the critical transition, as well as the above-critical temperature 'pseudo-gap' have been analyzed.Although the origin of the pseudo-gap is not completely understood, it can be considered as an independent phase transition in the substance prior to the transition to the zero resistance state and insusceptibility (or insensitivity) to external magnetic field in high-temperature superconductors. Features of multi-gap and gapless superconducting materials as well as their ability to further increase the temperature of supercritical transition are discussed. Large resources to create the necessary electron and phonon spectra in the process of high-temperature superconductivity formation are associated with the use of nanoscale structures and nanoparticles of conductors and dielectrics. Electrical conductive contacts between nanoparticles and tunnel chains of nanoclusters, where delocalized electron spectra form similar energy shells to the atomic or nuclear shells, play a significant part here. It is required to further investigate the occurrence of high-temperature superconductivity at the level of interphase layers (non-autonomous phases) in nanostructures containing a large fraction of the substance in this condition. It is essential to develop adequate methods for synthesis of nanoparticles of variable size, structure and morphology, as well as techniques for their consolidation that would ensure the preservation of superconductivity of individual nanoparticles, their chemical, thermal, magnetic and current stability in the dissipative processes with functional and fluctuation effects.

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“…Binary and quasi-binary yttrium carbides (in particular Th-doped yttrium carbide (Y 1Kx Th x )C 2 (T c Z17.0 K)) [2] have also attracted considerable attention since their T c values are close to those of A15 compounds [3,4]. Recently, our group has reported the discovery of superconductivity at 18 K in Y 2 C 3 [5].…”

Section: Introductionmentioning

confidence: 99%

Superconductivity in Y₂C₃with mediumT_c

Akutagawa

Akimitsu

2006

Science and Technology of Advanced Materials

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Recently, we have reported a relatively high-T c superconductivity in Y 2 C 3 at 18 K whose T c could be changed by synthesis conditions from 10 to 18 K [G. Amano, S. Akutagawa, T. Muranaka, Y. Zenitani, J. Akimitsu, Superconductivity at 18 K in yttrium sesquicarbide system, Y 2 C 3 J. Phys. Soc. Jpn. 73 (2004) 530.]. We synthesized a high-purity sample of the medium-T c phase in Y 2 C 3 and examined its physical properties in detail. From a specific heat measurement, DC(T c )/gT c value is calculated to be 6.50 and the superconducting gap is estimated to be 2D/k B T c Z5.40, indicating that the superconductivity in Y 2 C 3 can be described by an s-wave strong coupling regime. q

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Superconductivity in Transition-Metal Alloys

Cited by 55 publications

References 69 publications

Superconductivity and localization

Superconductivity and localization

High-temperature superconductivity: From macro- to nanoscale structures

Superconductivity in Y₂C₃with mediumT_c

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Superconductivity in Transition-Metal Alloys

Cited by 55 publications

References 69 publications

Superconductivity and localization

Superconductivity and localization

High-temperature superconductivity: From macro- to nanoscale structures

Superconductivity in Y2C3with mediumTc

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Superconductivity in Y₂C₃with mediumT_c