upper critical field

upper critical field

[¦əp·ər ¦krid·i·kəl ′fēld]
(solid-state physics)
The magnetic field strength above which a type II superconductor is completely normal. Symbolized Hc 2.
References in periodicals archive ?
From the theoretical point of view, the Werthamer-Helfand-Hohenberg (WHH) theory, for conventional low-[T.sub.c] superconductors, has been used to calculate [H.sub.c2](0) through the slope d[H.sub.c2]/dT in the vicinity of [T.sub.c], but this method gives only a rough estimation for [H.sub.c2](0) [13,15], for this reason it is important to develop theoretical models which describe and predict the upper critical field [H.sub.c2](0).
C is one of the determining characteristic parameters of superconductors; it cannot be measured directly, but it is possible to calculate it from zero temperature upper critical field [H.sub.c2](0) by the expression [H.sub.c2] = [[PHI].sub.0]/2[pi][[xi].sup.2], where [[PHI].sub.0] is the magnetic flux quantum [19].
In this work the relation between the d-wave gap and the specific heat obtained with the Volovik effect [18] is used to determine the upper critical field [H.sub.c2] as doping function for HTSC.
Finally, with the upper critical field [H.sub.c2], using the relation between [H.sub.c2] and [xi] at T = 0, the behavior of the coherence length [xi](0) with doping is obtained.
When a magnetic field is introduced, from the Volovik effect, the relation between the d-wave gap and the specific heat can be used to determine the upper critical field [H.sub.c2] as doping function [18].
[8] based on the t - ] model, with specific parameters values, have reproduced qualitatively the upper critical field, considering the interplay between the SC gap and the normal-state pseudogap.
[32] have determined the upper critical field [H.sub.c2] as function of x in bismuth-based cuprates by scaling of Nernst profiles.
The maximal upper critical field at the optimal doping (x = 0.15) obtained by Zhao et al.
In conclusion we determine the upper critical field [H.sub.c2] as doping function for HTSC using the relation between the d-wave gap and the specific heat obtained with the Volovik effect.
The upper critical field is extremely anisotropic, exceeding 16 Tesla for [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] while it reaches only 0.5 Tesla for [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] [6], the easy magnetization axis [2].
The symmetry of the superconducting gap has a small effect on the shape of the upper critical field, which was used by Hardy and Huxley [16] to suggest a superconducting state with a line of nodes in the parent system URhGe.
de Visser, "Unusual upper critical field of the ferromagnetic superconductor UCoGe," Physical Review Letters, vol.

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