The activation energy U(T,B) in high temperature superconductor

Abstract

We report on thermally assisted flux flow in YBa2Cu3O7-delta superconductor. The resistivity measurements rho(T,B) for many values of the magnetic field up to 14T in two directions with a dc weak transport current density were investigated in order to determine the activation energy and then understand the vortex dynamic phenomena and therefore deduce the vortex phase diagram. The apparent activation energy U0(T) is calculated using an Arrhenius relation. The measured results of the resistivity were adjusted to the modified thermally assisted flux flow model accounting for the temperature-field dependence of the activation energy U(T,B). The obtained values from the thermally assisted activation energy, exhibit a behavior similar to the one showed with the Arrhenius model, albeit larger than the apparent activation energy. The vortex glass model was used to obtain the vortex-glass transition temperature from linear fitting of [dLn(Rho)/dT]^-1 plots. In the course of this work thanks to the resistivity measurements we could locate the upper critical magnetic field Hc2(T), the irreversibility line Hirr(T) and the crossover field Hcrossover(T) . These three parameters allowed us to establish a phase diagram of the studied material where limits of each vortex phase are sketched in order to optimize its applicability as a practical high temperature superconductor used for diverse purposes.

Magnetic Penetration Depth and Coherence Length in a Single‐Crystal YBa2Cu3O7−δ

“…Similar behavior was obtained in works done by other researchers. [ 27,28,38–41 ] This considerable widening of the transition region in high‐temperature superconductors was attributed to the strength of fluctuations in these materials due to high values of T c , weak coherence length ξ , and large anisotropy. [ 42,43 ]…”

“…Similar behavior was obtained in works done by other researchers. [27,28,[38][39][40][41] This considerable widening of the transition region in high-temperature superconductors was attributed to the strength of fluctuations in these materials due to high values of T c , weak coherence length ξ, and large anisotropy. [42,43] These important fluctuations lead to weak pinning in HTSC, unlike the conventional type-II superconductors where pinning is very strong and thus the transition region is sharp.…”

“…Similar behavior was obtained in works done by other researchers. [27,28,41] The estimated slopes for B c2 are À12.5 and À3.2 T K À1 for B⊥c and B∥c, respectively. The B c2 (0) was estimated by using the conventional one-band Werthamer Helfand Hohenberg (WHH) theory [44] : B c2 (0) ¼ À0.69T c (dB c2 /dT), assuming that the upper critical field is limited by the orbital pair breaking effect.…”

Advanced materials for energy harvesting, storage, sensing and environmental engineering II

“…This Topical issue to the European Physical Journal À Applied Physics on Materials for Energy Harvesting, Storage, Sensing and Environmental Engineering intends to dress an updated and equilibrated picture of the multidisciplinary connections between energy and man-agement, as previous issues did [10][11][12][13]. This year's issue covers multidisciplinary areas of applied research into which Physics has a say: energy transfer, conversion and storage [14][15][16][17], fluid mechanics and microfluidics [18,19], materials [20][21][22]. Modelling and simulation complement the issue by providing understanding and prediction to experimental situations, with various approaches at multiple scales: nano, micro, meso and macroscopic [23][24][25][26][27].…”

“…Dans ce sens, l'activité scientifique a massivement bénéficié cette année de sa production passée et présente en termes de [10][11][12][13]. Le numéro de cette année couvre des domaines multidisciplinaires de recherche appliquée dans lesquels la physique a son mot à dire: transfert, conversion et stockage d'énergie [14][15][16][17], mécanique des fluides et microfluidique [18,19], matériaux [20][21][22]. La modélisation et la simulation complètent la problématique en permettant de comprendre et de prédire les situations expérimentales, avec différentes approches à plusieurs échelles: nano, micro, méso et macroscopique [23][24][25][26][27].…”