The Present State of the Theory of Superconductivity

Абрикосов, А. А.

doi:10.1070/pu1966v008n05abeh003031

Cited by 725 publications

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“…Nevertheless, by measuring the 3 rd harmonics of the AC susceptibility, this phase transition has been detected up to our highest available field (19 T), thus demonstrating the necessity of the higher harmonics analysis in studying these topics and moreover proving the validity of the theoretical predictions. Magnetic flux penetrates a type II superconductor in form of vortices, which distribute in a regular lattice in absence of defects [1,2]. Defects affect the lattice ordering, but prevent the dissipations associated to the vortex movement [2].…”

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Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

et al. 2006

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We report additional experimental evidences about the presence of an universal behavior in the Field-Temperature Phase Diagram of Type II Superconductors. This behavior is characterized by a phase transition in the vortex matter between the disordered and the Bragg Glass phase. The experimental detection of a Peak Effect phenomenon has been proved to be strictly connected to the existence of this phase transition. In this paper, we show the first observation of a Peak Effect in the compound Nb 3 Sn, by using 1 st harmonics of the AC magnetic susceptibility. Peak Effect has been detected at fields between 3T and 13T, whereas it is not observable at higher fields. This seems to be in contrast with the theoretical predictions of such a phase transition at all fields and, therefore, with the predicted universality in the magnetic behavior of the Type II superconductors. Nevertheless, by measuring the 3 rd harmonics of the AC susceptibility, this phase transition has been detected up to our highest available field (19 T), thus demonstrating the necessity of the higher harmonics analysis in studying these topics and moreover proving the validity of the theoretical predictions. Magnetic flux penetrates a type II superconductor in form of vortices, which distribute in a regular lattice in absence of defects [1,2]. Defects affect the lattice ordering, but prevent the dissipations associated to the vortex movement [2]. An universal field-temperature phase diagram has been supposed for all the type II superconductors with point defects. In this phase diagram a transition in the vortex lattice has been predicted, between a disordered phase and the Bragg Glass Phase [3,4]. This latter is characterized by a quasi long range order and a perfect topological order, in which the vortex lattice stills survives despite the presence of the pinning [3], as it has also been experimentally evidenced [5]. The disordered phase has been supposed to be again a glass phase ("multidomain glass"), but with a topological disorder at the largest length scales [4]. The critical current density, J c [6], generally decreasing with increasing temperature and/or magnetic field [2], shows a local maximum, known as Peak Effect [7], when the Disordered/Bragg Phase transition occurs. For this reason, the observation of the Peak Effect has been widely used to detect this phase transition [3]. The Peak Effect has been evidenced in various classes of type II superconductors, e.g. low-T c [8][9][10][11][12], high-T c [13][14][15], boro-carbides [16] and MgB 2 [17]; however, it has not been observed in Nb 3 Sn up to the present day, to the best of our knowledge. Nb 3 Sn crystallizes in the A15 type structure and is actually the most used material in the manufacturing of superconducting magnets at very high fields [18]. In the present work, measurements have been performed on a high quality Nb 3 Sn single crystal, furnished by M. Toyota [19] (Dimensions ≈ 3 x 1.32 x 0.43 mm 3 ). The sample was characterized by T c = 18.2 K, ΔT c = 0.1 K, T m = 38.84 K. A valu...

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mentioning

confidence: 99%

“…Magnetic flux penetrates a type II superconductor in form of vortices, which distribute in a regular lattice in absence of defects [1,2]. Defects affect the lattice ordering, but prevent the dissipations associated to the vortex movement [2].…”

mentioning

confidence: 99%

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

et al. 2006

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“…Planar Dirac fermions in the background of the Abrikosov-Nielsen-Olesen vortex [9,10] were studied in Ref. [11], and, recently, the results of this work have been used to consider the influence of the Kekulé distortion in the honeycomb lattice on the electronic properties of graphene [12,13].…”

Section: Introductionmentioning

confidence: 99%

Electronic properties of graphene with a topological defect

Sitenko

Власій

2007

Nuclear Physics B

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Various types of topological defects in graphene are considered in the framework of the continuum model for long-wavelength electronic excitations, which is based on the Dirac-Weyl equation. The condition for the electronic wave function is specified, and we show that a topological defect can be presented as a pseudomagnetic vortex at the apex of a graphitic nanocone; the flux of the vortex is related to the deficit angle of the cone. The cases of all possible types of pentagonal defects, as well as several types of heptagonal defects (with the numbers of heptagons up to three, and six), are analyzed. The density of states and the ground state charge are determined.

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“…As a concrete example of the theory with closed electric strings let us consider dual Abelian Higgs model 3 , where those are nothing, but the dual Abrikosov-Nielsen-Olesen strings [11]. This is also an example of the model which confines external point-like electric charges if there inserted any, just upon the formation of dual strings between those.…”

Section: Dimensional Reduction In the Theory Which Confines Closed Stmentioning

confidence: 99%

“…The bilocal correlator of densities of the vortex loops can then be calculated by the evaluation of the respective Gaussian integral [cf. the generating functional (11)] and in addition by taking explicitly into account the closeness of these objects with the use of the Hodge decomposition theorem (see the last Ref. of [14] for details).…”

Section: Dimensional Reduction In the Theory Which Confines Closed Stmentioning

confidence: 99%

Confining membranes and dimensional reduction

Antonov¹

2001

J. High Energy Phys.

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The dual theory describing the 4D Coulomb gas of point-like magnetically charged objects, which confines closed electric strings, is considered. The respective generalization of the theory of confining strings to confining membranes is further constructed. The same is done for the analogous SU(3)-inspired model. We then consider a combined model which confines both electric charges and closed strings. Such a model is nothing, but the mixture of the above-mentioned Coulomb gas with the condensate of the dual Higgs field, described by the dual Abelian Higgs model. It is demonstrated that in a certain limit of this dual Abelian Higgs model, the system under study undergoes naively the dimensional reduction and becomes described by the (completely integrable) 2D sine-Gordon theory. In particular, owing to this fact, the phase transition in such a model must be of the Berezinskii-Kosterlitz-Thouless type, and the respective critical temperature is expressed in terms of the parameters of the dual Abelian Higgs model. However, it is finally discussed that the dimensional reduction is rigorously valid only in the strong coupling limit of the original 4D Coulomb gas. In such a limit, this reduction transforms the combined model to the 2D free bosonic theory. *

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The Present State of the Theory of Superconductivity

Cited by 725 publications

References 0 publications

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

Electronic properties of graphene with a topological defect

Confining membranes and dimensional reduction

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