Superconductivity in MgB2

Muranaka, Toshiya; Zenitani, Yuji; Shimoyama, Jun–ichi; Akimitsu, Jun

doi:10.1007/3-540-27294-1_26

Cited by 9 publications

(12 citation statements)

References 210 publications

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“…This discovery stimulated global interest seeking higher T c and uncovering the basic physics [2]. MgB 2 attracts a lot of attention from both condensed matter experimentalists and theorists [1,2,3].…”

Section: Introductionmentioning

confidence: 99%

“…Its high T c comes from the exceptionally high vibrational energies in the graphite-like boron planes and thus MgB 2 appears to obey conventional models of superconductivity. This relatively simple view (as compared to HTS) opens up a wide range of practical opportunities [2]. Based on various physical property measurements, important critical parameters of the compound viz., critical superconducting temperature (T c ), coherence length (ξ), penetration depth (λ), critical current (J c ) and lower/upper critical fields H c1 /H c2 have already been determined and reviewed [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…It contains graphite-type boron layers, which are separated by hexagonal close-packed layers of magnesium. The magnesium atoms are located at the center of hexagons formed by boron and donate their electrons to the boron planes [1,2]. Similar to graphite, MgB 2 exhibits anisotropy in the B-B length:…”

Section: Introductionmentioning

confidence: 99%

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A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB₂, AlB₂ AND AgB₂ SYSTEMS

et al. 2006

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB₂, AlB₂ AND AgB₂ SYSTEMS

et al. 2006

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“…Such a case can be applied to the superconductivity in liquid hydrogen [12]. We go beyond the weak coupling limit of γ, which would be significant for the two-gap superconductivities in solid state, e.g., MgB 2 [7]. In Eq.…”

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confidence: 99%

“…For the string with sufficiently large L st , N con would be well approximated by the random walk result and we obtain N con ≃ µ Lst/ξ . Table 1: Parameters which would be relevant for MgB2 [7] ξ(0)/λ(0) 0.32…”

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confidence: 99%

Deconfinement of vortices with continuously variable fractions of the unit flux quanta in two-gap superconductors

2007

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Abstract. -We propose a new stage of confiment-decofinment transition, which can be observed in laboratory. In two-gap superconductors (SCs), two kinds of vortex exist and each of them carries a continuously variable fraction of the unit flux quanta Φ0 = hc/2e. The confined state of these two is a usual vortex and stable in the low temperature region of the system under a certain magnetic field above Hc1. We see an analogy to quarks in a charged pion. An entropy gain causes two fractional vortices to be deconfined above a certain temperature.Introduction. -Topological defects furnish fascinating problems in physics, and keep attracting a lot of concerns. In general, they lead the quantization of physical quantities. Vortex is one of the most important example of topological defects [1]. It is well known that in superconductors (SCs), the requirement that the order parameter is a single-valued function guarantees the quantization of the magnetic flux of a vortex in the unit of Φ 0 = hc/2e.The fractionalization of topologically quantized numbers have also been researched extensively in many different contexts [2]. Vortices with fractional fluxes have been discussed in p-wave superfluid Here we discuss vortex state in two-gap SCs [6] which has two superconducting gaps on two separate Fermi surfaces. The two-gap superconductivity can be seen in a lot of SCs in solid state and has been paid special attention. MgB 2 is a recent typical textbook [7]. The possibility of the two-gap superconducting state is also pointed out in 2H-NbSe 2 [8], PrOs 4 Sb 12 [9], Y 2 C 3 [10], Ca-doped YBCO [11], and liquid hydrogen [12]. The fractionalization of the flux quanta has also been discussed in two-gap SCs [13,14]. Tanaka considered a wire ring and showed that a trapped flux in the ring can be an arbitrary fraction of Φ 0 [13]. Babaev considered a planer geometry and dis-

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Magnetic Field Sources

Kitanovski

Tušek

Tomc

et al. 2014

Magnetocaloric Energy Conversion

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In this chapter we describe some of the most important issues that relate to the sources for magnetic fields. We will try to provide information for engineers about the different possible magnetic field sources with respect to their application in magnetocaloric energy conversion. However, the main emphasis will be on permanent magnets and their assemblies. This is due to the fact that other kinds of magnetic field sources, for instance, electric resistive coils (electromagnets) operate with a rather low efficiency. The efficiency in electromagnets in terms of thermodynamics must be considered as the ratio of the energy output (magnetization energy) and the energy input to the coil. The current passing through the coiled wires in an electromagnet will induce Joule heating, due to the electric resistance. Not only will a loss of valuable energy occur, but the magnetic field source will, in most cases, also require cooling, especially in cases where a high magnetic flux density is required. In superconducting magnets, which can be treated as a special class of electromagnets, the current may be kept circulating through the wires of a coil without electrical resistance losses. However, in order to keep the superconducting magnet operating, a cryogenic system is required to provide cooling for the superconducting electrical coils. Namely, there is no practical application of a room-temperature superconducting material. There are, however, some indicators that this could be possible [1][2][3][4][5]. And if this happens in future, this chapter will unfortunately (or fortunately) not be of much use, but the application will open up an unbelievable range of applications, which will certainly change our way of life, including magnetocaloric energy conversion.The reader should note that the magnetic field source is the most expensive part of a magnetic refrigerator or a heat pump, especially if those are based on permanent or superconducting magnets. Therefore, the optimal design of a magnetic field source is crucial for obtaining a cost-effective and energy-efficient device.

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Superconductivity in MgB2

Cited by 9 publications

References 210 publications

A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB₂, AlB₂ AND AgB₂ SYSTEMS

A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB₂, AlB₂ AND AgB₂ SYSTEMS

Deconfinement of vortices with continuously variable fractions of the unit flux quanta in two-gap superconductors

Magnetic Field Sources

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Superconductivity in MgB2

Cited by 9 publications

References 210 publications

A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB2, AlB2 AND AgB2 SYSTEMS

A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB2, AlB2 AND AgB2 SYSTEMS

Deconfinement of vortices with continuously variable fractions of the unit flux quanta in two-gap superconductors

Magnetic Field Sources

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A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB₂, AlB₂ AND AgB₂ SYSTEMS

A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB₂, AlB₂ AND AgB₂ SYSTEMS