Dynamic of vortices in YBa₂Cu₃O_7–δ single crystal near the temperature of the vortex glass transition by the use of voltage noise measurements

Abstract

Dynamic of vortices in YBaWe have studied the voltage noise V n and the voltage noise spectral density S V of YBa 2 Cu 3 O 7-δ superconductor in the regime of high magnetic field. Our studies were performed in a large range of temperature T (70 K-90 K) covering the vortex-glass -vortex-liquid transition which appears at T g temperature. The sample is driving by a current I = 1 nA, under a different high magnetic fields H (2.4 T, and 5 T).The noise spectral density noted S V (f) exhibits a 1/f α . Approaching T g the vortex glass transition, the voltage noise spectral density S V (T) is found to vanish critically according to the critical power law S V ∝ (T-T g )x , with x = 1.64 ± 0.1 which represents the critical exponent. The behaviour exhibited by S v (T) cannot be simply interpreted by thermal fluctuations as we conclude by comparing S V (T) with (dR/dT)