Vortex Phases

Giamarchi, Thierry; Bhattacharya, S.

doi:10.1007/3-540-45649-x_13

Cited by 69 publications

(88 citation statements)

References 111 publications

(202 reference statements)

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“…Most high-T c materials behave in a magnetic field as type-II superconductors, with further complications due to the broader phase space-in terms of temperature T and field H-in comparison to conventional type-II superconductors. [1][2][3] This leads to several possibilities for the mixed phase, where magnetic flux penetration is incomplete. As first discussed by Abrikosov for conventional superconductors, 4 flux is quantized and carried by vortex lines which are arranged in the form of a lattice.…”

Section: Introductionmentioning

confidence: 99%

Grain boundaries in vortex matter

2005

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We explore the statistical properties of grain boundaries in the vortex polycrystalline phase of type-II superconductors. Treating grain boundaries as arrays of dislocations interacting through linear elasticity, we show that self-interaction of a deformed grain boundary is equivalent to a nonlocal long-range surface tension. This affects the pinning properties of grain boundaries, which are found to be less rough than isolated dislocations. The presence of grain boundaries has an important effect on the transport properties of type-II superconductors as we show by numerical simulations: our results indicate that the critical current is higher for a vortex polycrystal than for a regular vortex lattice. Finally, we discuss the possible role of grain boundaries in vortex lattice melting. Through a phenomenological theory we show that melting can be preceded by an intermediate polycrystalline phase.

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Section: Introductionmentioning

confidence: 99%

Grain boundaries in vortex matter

2005

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“…In real superconductors the equilibrium vortex structures are controlled by the competition between vortex-vortex interactions and vortex-disorder interactions [2]. As the disorders become important, the ordered Abrikosov mixed state will change into disordered liquid due to thermal fluctuations, or into glass states due to pinning [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Simulation of the phase diagram of magnetic vortices in two-dimensional superconductors: evidence for vortex chain formation

Xu¹,

Fangohr²,

Gu³

et al. 2014

J. Phys.: Condens. Matter

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We study the superconducting vortex states induced by the interplay of long-range Pearl repulsion and short-range intervortex attraction using Langevin dynamics simulation. We show that at low temperature the vortices form an ordered Abrikosov lattice both in low and high fields. The vortices show distinctive modulated structures at intermediate fields depending on the effective intervortex attraction: ordered vortex chain and Kogame-like vortex structures for weak attraction; bubble, stripe and antibubble lattices for strong attraction. Moreover, in the regime of the chain state, the vortices display structural transitions from chain to labyrinthine (or disordered chain) and/or to disordered state depending on the strength of disorders.

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“…Furthermore, the occurrence of PE was explained as evidence for a Bragg glass transition or an order-disorder (OD) transition [2,5,9,16]. The OD transition was suggested to be a thermodynamic phase transition induced by thermal fluctuations or pinning centers [2], which has been confirmed experimentally by the direct structural observation of the vortex lattice, such as small angle neutron scattering (SANS) [9], and muon spin relaxation [17]. Also, the investigation of the reversibility of the OD transition provided strong support for its thermodynamical nature [18].…”

mentioning

confidence: 99%

“…The PE has widely been observed in a variety of low and high temperature superconductors by different experimental techniques [2], such as transport [3][4][5], magnetization [6,7], and ac-susceptibility [8][9][10]. It was proposed long ago that the PE originated from softening of the elastic moduli of vortex lattice [1], which caused by the competitions between elastic energy E el , pinning energy E pin of vortex lattice and the energy of thermal fluctuations E th [11].…”

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confidence: 99%

“…The PE was recently shown to appear naturally at the crossover from weak collective to strong pinning [15]. Further calculations showed that the "Bragg glass" phases exist to be a quasi-long-range ordered vortex lattice on a length scale r ≫ R c [2]. Furthermore, the occurrence of PE was explained as evidence for a Bragg glass transition or an order-disorder (OD) transition [2,5,9,16].…”

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confidence: 99%

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Peak Effect in the Critical Current of Type II Superconductors with Strong Magnetic Vortex Pinning

Fangohr

et al. 2008

Phys. Rev. Lett.

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We have performed 2D-Langevin simulations studying the peak effect (PE) of the critical current taking into account the temperature dependence of the competing forces. We observe and report that the occurrence of the PE results from the competition of vortex-vortex interactions and vortex-pin interactions and thermal fluctuations which have different temperature dependencies. The simulations reveal that the PE can only take place for certain pinning strengths, densities of pinning centers and driving forces, which is in good agreement with experiments. No apparent vortex order-disorder transition is observed across the PE regime. Besides, the PE is a dynamical phenomenon and thermal fluctuations can speed up the process for the formation of the PE.PACS numbers: 74.25. Fy, 74.25.Qt One pronounced phenomenon in type-II superconductors is the so called peak effect (PE), which is the appearance of a peak in the critical current density J c before decreasing to 0 with increasing temperature or field [1]. The PE has widely been observed in a variety of low and high temperature superconductors by different experimental techniques [2], such as transport [3][4][5], magnetization [6,7], and ac-susceptibility [8][9][10]. It was proposed long ago that the PE originated from softening of the elastic moduli of vortex lattice [1], which caused by the competitions between elastic energy E el , pinning energy E pin of vortex lattice and the energy of thermal fluctuations E th [11]. Considering the competition between the strength of vortex lattice and the pinning force of isolated pinning center, Labusch showed that J c > 0 only if the pinning force dominates over the strength of vortex lattice, otherwise J c = 0 [12]. According to the Labusch criterion the weak pinning centers in superconductors cannot pin the vortex lattice. Larkin and Ovchinnikov showed that weak pinning centers can act collectively in the correlation volume V c (=L c R 2 c , where L c and R c are the longitudinal and transverse correlation lengths respectively), where the vortices are of long-range order, reducing much the Labusch criterion [13]. In the collective pinning theory the PE was interpreted as resulting from the abrupt decrease of V c due to the reduction in elastic interaction [14]. The PE was recently shown to appear naturally at the crossover from weak collective to strong pinning [15]. Further calculations showed that the "Bragg glass" phases exist to be a quasi-long-range ordered vortex lattice on a length scale r ≫ R c [2]. Furthermore, the occurrence of PE was explained as evidence for a Bragg glass transition or an order-disorder (OD) transition [2,5,9,16]. The OD transition was suggested to be a thermodynamic phase transition induced by thermal fluctuations or pinning centers [2], which has been confirmed experimentally by the direct structural observation of the vortex lattice, such as small angle neutron scattering (SANS) [9], and muon spin relaxation [17]. Also, the investigation of the reversibility of the OD transition provided st...

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Vortex Phases

Abstract: These lecture notes are meant to provide a pedagogical introduction, and present the latest theoretical and experimental developments on the physics of vortices in type II superconductors.

Cited by 69 publications

References 111 publications

Grain boundaries in vortex matter

Grain boundaries in vortex matter

Simulation of the phase diagram of magnetic vortices in two-dimensional superconductors: evidence for vortex chain formation

Peak Effect in the Critical Current of Type II Superconductors with Strong Magnetic Vortex Pinning

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