Vortex-Motion-Induced Voltage Noise inYBa2Cu3O7−δSingle Crystals

We have investigated vortex motion below the quasistatic melting transition in a detwinned ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ single crystal by measuring the differential resistance and the voltage noise. With the magnetic field parallel to the copper-oxygen planes and the large, flat surface of the sample, the noise power spectrum permits us to deduce that the surfaces are the dominant source of the noise and that the vortices appear to be flowing in channels. In certain regimes, the noise power spectrum exhibits unusually sharp and distinct peaks which are periodic in frequency.