Dynamic of vortices in YBa2Cu3O7-δ single crystal near the temperature of the vortex glass transition by the use of voltage noise measurements

We have studied the voltage noise Vn and the voltage noise spectral density S-v of YBa2CU3O7-delta 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(alpha). 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 proportional to (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)2 curve.