Ginzburg-Landau theory for superconductors

Cyrot, M.

doi:10.1088/0034-4885/36/2/001

Cited by 183 publications

(126 citation statements)

References 46 publications

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“…4, which shows that H irr decreases gradually from nearly 13 T to 11.8 T at T = 5 K for P = 1.2 GPa, which is ascribed to the observed J c suppression. , where is the slope of the fitted line and its value depends on the magnetic field [37][38][39]. The exponent in our case is found to be nearly same at different pressures, and its values are 1.63, 2.22, and 2.65 at fields of 0, 2.5, and 5 T, respectively.…”

supporting

confidence: 51%

Hydrostatic pressure induced transition fromδT_Ctoδℓpinning mechanism in MgB₂

Shabbir¹,

Wang²,

Ghorbani³

et al. 2015

Supercond. Sci. Technol.

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The impact of hydrostatic pressure up to 1.2 GPa on the critical current density (J c ) and the nature of the pinning mechanism in MgB 2 have been investigated within the framework of the collective theory. We found that the hydrostatic pressure can induce a transition from the regime where pinning is controlled by spatial variation in the critical transition temperature (δT c ) to the regime controlled by spatial variation in the mean free path (δℓ). Furthermore, T c and low field J c are slightly reduced, although the J c drops more quickly at high fields than at ambient pressure. We found that the pressure raises the anisotropy and reduces the coherence length, resulting in weak interaction of the vortex cores with the pinning centres. Moreover, the hydrostatic pressure can reduce the density of states [N s (E)], which, in turn, leads to a reduction in the critical temperature from 39.7 K at P = 0 GPa to 37.7 K at P = 1.2 GPa.Magnesium diboride (MgB 2 ) is a promising superconducting material which can replace conventional low critical temperature (T c ) superconductors in practical applications, due to its relatively high T c of 39 K, strongly linked grains, rich multiple band structure, low fabrication cost, and especially, its high critical current density (J c ) values of 10 5 -10 6 A/cm 2 [1-9]. Numerous studies have been carried out in order to understand the vortex-pinning mechanisms in more detail, which have led to real progress regarding the improvement of J c . There are two predominant mechanisms, c pinning, which is associated with spatial fluctuations of the T c , and ℓ pinning, associated with charge carrier mean free path (ℓ) fluctuations [10][11][12][13][14].Very recently, our team have found that hydrostatic pressure is a most effective approach to enhance J c significantly in iron based superconductors, as the pressure can induce more point pinning centres and also affect the pinning mechanism [15]. Therefore, it is natural to investigate the impact of hydrostatic pressure on J c and flux pinning mechanisms in MgB 2 . Previous studies have shown that pressure of 1 GPa can reduce T c , but only by less than 2 K in MgB 2 . This is a very insignificant reduction as compared to the other approaches (i.e. chemical doping and irradiation) which are mainly used for J c enhancement [16]. For instance, chemical doping can significantly enhance J c in MgB 2 , but with a considerable degradation of T c ; carbon doping can reduce T c from 39 K to nearly as low as 10 K, for carbon content up to 20% [17][18][19][20][21][22]. Similarly, the irradiation method can improve J c in MgB 2 , but it reduces T c values significantly (by more than 20 K in some cases) [23][24][25][26][27]. Correspondingly, the chemical doping and irradiation methods can also change the nature of the pinning mechanism in MgB 2 [24,[28][29][30]. The determination of J c and the flux pinning mechanism under hydrostatic pressure is also an important step to probe the mechanism of superconductivity in more detail in MgB 2 . It is very i...

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supporting

confidence: 51%

Hydrostatic pressure induced transition fromδT_Ctoδℓpinning mechanism in MgB₂

Shabbir¹,

Wang²,

Ghorbani³

et al. 2015

Supercond. Sci. Technol.

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“…Provatas and Elder (2010). Such modeling has found many applications, especially in the areas of magnetic field theory where it has been found useful for providing predictive models (Cyrot 1973;Berger 2005;BarbaOrtega et al 2009;Cao et al 2013;Gonçalves et al 2014). But more importantly for the present application it has also proven to be an efficient methodology to model and predict microstructure evolution in materials.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics simulations of liquid crystalline phases of dodecyltrimethylammonium chloride

Kocherbitov

2015

Journal of Molecular Liquids

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The formation of a second phase in presence of a crack in a crystalline material is modelled and studied for different prevailing conditions in order to predict and a posteriori prevent failure, e.g. by delayed hydride cracking. To this end, the phase field formulation of Ginzburg-Landau is selected to describe the phase transformation, and simulations using the finite volume method are performed for a wide range of material properties. A sixth order Landau potential for a single structural order parameter is adopted because it allows the modeling of both first and second order transitions and its corresponding phase diagram can be outlined analytically. The elastic stress field induced by the crack is found to cause a space-dependent shift in the transition temperature, which promotes a second-phase precipitation in vicinity of the crack tip. The spatiotemporal evolution during nucleation and growth is successfully monitored for different combinations of material properties and applied loads. Results for the second-phase shape and size evolution are presented and discussed for a number of selected characteristic cases. The numerical results at steady state are compared to mean-field equilibrium solutions and a good agreement is achieved. For materials applicable to the model, the results can be used to predict the evolution of an eventual second-phase formation through a dimen-

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“…In the frame of the theory of liquids the model of liquid helium proposed by Landau [142] can be compared to the suggested model. Within this model the liquid appears as made up of two phases, one coherent (namely having components oscillating in phase), the other non-coherent (namely having independent components as in a gas).…”

Section: Quantum Mechanical/quantumelectrodynamical Viewpointmentioning

confidence: 99%

Can a Century Old Experiment Reveal Hidden Properties of Water?

Fuchs¹

2010

Water

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Abstract:In 1893 Sir William Armstrong placed a cotton thread between two wine glasses filled with chemically pure water. After applying a high voltage, a watery connection formed, and after some time, the cotton thread was pulled into one of the glasses, leaving a rope of water suspended between the two glasses. Although being a very simple experiment, it is of special interest since it comprises a number of phenomena currently tackled in modern water science like electrolysis-less charge transport and nanobubbles. This work gives some background information about water research in general and describes the water bridge phenomenon from the viewpoint of different fields such as electrohydrodynamics and quantum field theory. It is shown that the investigation of the floating water bridge led to new discoveries about water, both in the macroscopic and microscopic realm -but these were merely "hidden" in that sense that they only become evident upon application of electric fields.

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Ginzburg-Landau theory for superconductors

Cited by 183 publications

References 46 publications

Hydrostatic pressure induced transition fromδT_Ctoδℓpinning mechanism in MgB₂

Hydrostatic pressure induced transition fromδT_Ctoδℓpinning mechanism in MgB₂

Molecular dynamics simulations of liquid crystalline phases of dodecyltrimethylammonium chloride

Can a Century Old Experiment Reveal Hidden Properties of Water?

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Ginzburg-Landau theory for superconductors

Cited by 183 publications

References 46 publications

Hydrostatic pressure induced transition fromδTCtoδℓpinning mechanism in MgB2

Hydrostatic pressure induced transition fromδTCtoδℓpinning mechanism in MgB2

Molecular dynamics simulations of liquid crystalline phases of dodecyltrimethylammonium chloride

Can a Century Old Experiment Reveal Hidden Properties of Water?

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Hydrostatic pressure induced transition fromδT_Ctoδℓpinning mechanism in MgB₂

Hydrostatic pressure induced transition fromδT_Ctoδℓpinning mechanism in MgB₂