Vortex pinning by twin boundaries and CuO-planes in HTSC single crystals investigated by torque magnetometry

Hergt, R.; Andrä, W.; Fischer, K.

doi:10.1016/0921-4534(91)91223-q

Cited by 2 publications

(3 citation statements)

References 5 publications

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“…The effect of a magnetic field on the BKT transition is investigated by Martynovich (1994), who finds that the transition can become of first order at high fields. Fischer (1995b) shows that point pinning practically does not change the BKT transition, see also Fischer (1991Fischer ( , 1992a. Yazdani et al (1993) observe that in an amorphous MoGe film the BKT melting is not strongly influenced by pinning when the order in the vortex lattice is sufficiently large, but Hsu and Kapitulnik (1992) in detailed studies of ultrathin clean monocrystalline Nb films see a strong influence of pinning on the BKT transition.…”

Section: D Melting and The Kosterlitz-thouless Transitionmentioning

confidence: 97%

“…Pancake vortices. When B a is nearly along the c-axis the flux lines formally consist of a stack of 2D point vortices, or pancake vortices (Efetov 1979, Artemenko and Kruglov 1990, Guinea 1990, Clem 1991, Buzdin and Feinberg 1990, Fischer 1991 which have their singularity (the zero of ψ and infinity of ∇φ) only in one layer. The field of a single point vortex with centre at r i = 0 is confined to a layer of thickness ≈ 2λ ab .…”

Section: Layered Superconductorsmentioning

confidence: 99%

“…The critical current density J c in layered HTSC's is highly anisotropic (Barone et al 1990, Pokrovsky et al 1992, Balents and Nelson 1994 since flux lines are pinned much more strongly when they are parallel to the Cu-O layers (Tachiki and Takahashi 1989, Schimmele et al 1988, Senoussi et al 1993, Nieber and Kronmüller 1993a, Koshelev and Vinokur 1995. In YBCO planar twin-boundaries cause anisotropic pinning (Kwok et al 1990, Liu et al 1991, Hergt et al 1991, Fleshler et al 1993, Vlasko-Vlasov et al 1994b. Anisotropic pinning by linear defects (e.g.…”

Section: Theories Of Pinningmentioning

confidence: 99%

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The flux-line lattice in superconductors

1995

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Magnetic flux can penetrate a type-II superconductor in form of Abrikosov vortices (also called flux lines, flux tubes, or fluxons) each carrying a quantum of magnetic flux φ 0 = h/2e. These tiny vortices of supercurrent tend to arrange in a triangular flux-line lattice (FLL) which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-T c superconductors (HTSC's) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft mainly because of the large magnetic penetration depth λ: The shear modulus of the FLL is c 66 ∼ 1/λ 2 , and the tilt modulus c 44 (k) ∼ (1 + k 2 λ 2 ) −1 is dispersive and becomes very small for short distortion wavelength 2π/k ≪ λ. This softness is enhanced further by the pronounced anisotropy and layered structure of HTSC's, which strongly increases the penetration depth for currents along the c-axis of these (nearly uniaxial) crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may "melt" the FLL and cause thermally activated depinning of the flux lines or of the two-dimensional "pancake vortices" in the layers. Various phase transitions are predicted for the FLL in layered HTSC's. Although large pinning forces and high critical currents have been achieved, the small depinning energy so far prevents the application of HTSC's as conductors at high temperatures except in cases when the applied current and the surrounding magnetic field are small.

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Section: D Melting and The Kosterlitz-thouless Transitionmentioning

confidence: 97%

Section: Layered Superconductorsmentioning

confidence: 99%

Section: Theories Of Pinningmentioning

confidence: 99%

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The flux-line lattice in superconductors

1995

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Driving and pinning forces acting on vortices in layered superconductors

1993

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The vortex structure and the distribution of the transport current in a layered superconductor consisting of an alternate stack of strongly and weakly superconducting layers are theoretically studied within the framework of the Cxinzburg-Landau theory. It is assumed that in the superconductor the coherence length is comparable to the layer thickness and the penetration depth is much longer than the thickness. The present theory predicts that the superconducting current mainly Aows in the strongly superconducting layer, while the vortex center lies in the weakly superconducting layer. As a result the driving force acting on the vortex becomes extremely weak, since the small current density in the weakly superconducting layer is responsible for the force. Some behavior of the critical current in the cuprate superconductors YBa2Cu307 q and Bi2SrzCaCu208+q may be explained with the present theory.

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Vortex pinning by twin boundaries and CuO-planes in HTSC single crystals investigated by torque magnetometry

Cited by 2 publications

References 5 publications

The flux-line lattice in superconductors

The flux-line lattice in superconductors

Driving and pinning forces acting on vortices in layered superconductors

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