Measurements of transport properties and noise power spectral densities for Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ single crystals

The authors measured the current-voltage characteristics of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ single crystals along the a-b plane and observed the behavior of the Kosterlitz-Thouless (K-T) transition. The noise power spectral density, S/sub v/(f), near the K-T transition temperature was studied in detail by changing the temperature, magnetic field, and current S/sub v/(f) at temperatures above the K-T transition temperature T/sub KT/ shows a 1/f behavior, regardless of the external magnetic field. However, near T/sub KT/, the S/sub v/(f) deviates markedly from the 1/f behavior for the experimental frequency range. It is believed that the anomalous variation of frequency dependence near T/sub KT/ originates from the fluctuation effect of the vortex-antivortex pairs, i.e., their annihilation-creating fluctuations.<
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