Continuum theory of the mixed-state and surface Joule effects in type-II superconductors

Hocquet, Thierry; Mathieu, P.; Simon, Y.

doi:10.1103/physrevb.46.1061

Cited by 63 publications

(72 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Thus, by assuming that the vortex array moves uniformly while maintaining its critical-state configuration, such as sketched in Fig. 1 (b), MS could explain most of the dc properties, in particular the dc Joule effect [11,14]. Of course, the rigid and uniform motion of VL, especially near the surface, is unrealistic; it only represents a timeaverage picture of the vortex flow.…”

mentioning

confidence: 95%

See 1 more Smart Citation

Critical-current fluctuations and flux-flow noise in type-II superconductors

Plaçais¹,

Mathieu²,

Simon³

1993

Phys. Rev. Lett.

Self Cite

View full text Add to dashboard Cite

By relying on a recent theory of transport in the mixed state and a related model of pinning in soft materials, the instantaneous critical current is introduced as a well-defined part I\ of the total constant current. This nondissipative and time-dependent I\ is assumed to be randomly distributed near the sample surface, and is described as a 2D turbulent homogeneous flow. Auto-and cross-correlation functions of both voltage and magnetic field noises are predicted and are in full agreement with experiments.PACS numbers: 74.60.Ge, 74.60Jg Flux-flow noise has been extensively studied, particularly during the 1960's and 1970's [1-6]. The spectrum and amplitude of the noise voltage dV(t), typically 10 ~^-10 "'' V/(Hz) ^/^ in the 0-10 kHz bandwidth, were regarded as significant parameters revealing the more or less irregular motion of vortex lines (VL) in the presence of pinning. The reader is referred to the excellent critical review by Clem [7]. In view of the experimental difficulties and the increasing intricacy of interpretations, this scope has been practically discarded since about 1980.It should be noted that soft samples were used, classically shaped as foils or strips perpendicular to the applied magnetic field. Low to moderate critical currents /^ are required to avoid spurious sources of noise due to excessive dissipation, such as flicker noise [7]. Therefore, at working temperatures (4.2 K [1,2,5] or close to the X point [6]), the authors had to operate at the onset of the /-K curve; in this region, where flux flow is essentially inhomogeneous along the sample [8], measurements yield unreliable results.Recently [9], we have reconsidered the problem of noise, both theoretically and experimentally. We have performed a series of experiments in superfluid helium in order to widely explore the flux-flow regime. Voltage noise, magnetic field noise around the sample, and thermal Joule noise [10] were investigated, as well as their cross correlations. By relying on a phenomenological theory of vortex motion, recently published by two of us, Mathieu and Simon (MS) [11], we were able to work out a consistent theory of noise, the principle of which is brought forward in this Letter.Roughly speaking, two mechanisms have been advanced to account for the voltage noise quantitatively. In their pioneering work, van Ooijen and van Gurp [1] assumed that flux bundles nucleated randomly at one edge and moved rigidly across the sample with constant velocity VL. This process gives rise to a time sequence of statistically independent pulses, the cutoff' frequency of the noise spectrum being related to the time of flight of bundles. This analogy with the electronic "shot noise" was attractive, but more and more adjustable parameters were introduced to fit the data; besides the flux bundle size ipb, others include the fraction of pinned vortices [2], or a distribution of subpulse times [6]. Somewhat artificially, ipb is found to be a rapidly decreasing function of current, falling off* below the flux quantum <^o [2,6]. Moreov...

show abstract

mentioning

confidence: 95%

“…Here we need to recall the main outlines of the MS phenomenological theory [11,14]. The mixed state is regarded as a continuum on the scale of the vortex spacing a, and the vortex array is described locally by the vector G>=«v?ov, where v is a unit vector along VL.…”

mentioning

confidence: 99%

Critical-current fluctuations and flux-flow noise in type-II superconductors

Plaçais¹,

Mathieu²,

Simon³

1993

Phys. Rev. Lett.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The mixed state microwave response, which includes vortex dynamics, is quite intricate, since it emerges from the interplay between the currents excited by the applied microwave fields and vortices set in motion by these currents. Many authors considered this issue, providing models which take into accounts various aspects [20][21][22][23][24]. Following Coffey-Clem (CC) approach [21], the whole complex resistivityρ can be written down as follows:…”

Section: Experimental Technique and Data Analysismentioning

confidence: 99%

Microwave properties of DyBCO monodomain in the mixed state and comparison with other RE-BCO systems

Pompeo

Rogai

Ausloos

et al. 2011

Physica C: Superconductivity and its Applications

View full text Add to dashboard Cite

show abstract

“…9). Physically, this solution appears in the case of vortex pinning by the surface roughness [25]. The main idea is that the surface disorder (a quite standard surface roughness) allows, thanks to boundary conditions, for the flow of non dissipative superficial current (i c (A/cm) = I c /2W ).…”

mentioning

confidence: 99%

On voltage-current characteristics and critical current in Bi-2212

Pautrat¹,

Simon²,

Scola³

et al. 2005

Eur. Phys. J. B

View full text Add to dashboard Cite

V(I) characteristics have been performed in a monocrystalline microbridge of Bi[P b] − 2212. The vortex phase diagram has been greatly investigated. Linear but non-ohmic Voltage(Current) (V(I)) curves with well defined critical current have been observed. A departure from this behavior is observed near the peak effect where an out of equilibrium high threshold current can be stabilized. At high temperature, the critical current persists in the "liquid" state despite the dissipation at the lowest bias. Some implications of these results are discussed. In particular, it is proposed that the surface disorder, rather than the bulk disorder, is responsible for the vortex pinning in this sample. The generic vortex phase diagram in cuprates is now described in terms of into different thermodynamic phases of vortex [1]. The main idea is that an ordered Vortex Lattice (VL) is present at low field and low temperature, and that it develops into a phase possessing a degraded order when the thermal fluctuations or the static disorder are increased. This corresponds respectively to (ordered solid/liquid) and (ordered solid/disordered solid) transitions. The strong experimental facts which have justified these ideas are the disappearance of the vortex pinning in the "liquid" phase and the increase of this vortex pinning (the peak effect) when crossing the disordering transition. The highly anisotropic cuprate Bi-2212 can be taken as a representative sample where these three states can appear. Nevertheless, recent experiments suggest to qualify this point of view. Indeed, it has been found that both the high field and the high temperature properties can be interpreted with the same state of vortex matter, meaning that no difference between them should be presupposed [2,3]. Another striking result is that VL translational order is not a good order parameter to characterize the first order transition [4], whereas one could have expected the contrary for a genuine melting. From an experimental point of view, the VL behavior in Bi-2212 has been tackled at low field by magneto-optic imaging or local ac probes [2,3], which are sensitive to pinning induced screening currents on the surface of the samples. If the magnetic field is increased, the limited resolution of the above-cited experiments strongly restricts their ability to give information on the VL pinning and dynamical properties. One complementary and easily understandable experiment is the measure of a voltage versus current (V(I)) curve. The critical current I c , which gives the pinning ability of the medium, can be extracted without the need of complicated and possibly unjustified assumptions. Furthermore, it has been shown by numerous theories and simulations [5,6,7] that the nature of the VL

show abstract

Continuum theory of the mixed-state and surface Joule effects in type-II superconductors

Cited by 63 publications

References 19 publications

Critical-current fluctuations and flux-flow noise in type-II superconductors

Critical-current fluctuations and flux-flow noise in type-II superconductors

Microwave properties of DyBCO monodomain in the mixed state and comparison with other RE-BCO systems

On voltage-current characteristics and critical current in Bi-2212

Contact Info

Product

Resources

About