Measurements of noise spectral densities for a high-Tc superconductor: Single-crystal Bi2Sr2CaCu2Ox.

Abstract

The noise power spectral density for a ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{1}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{\mathit{x}}$ single crystal has been examined as a function of magnetic field, temperature, and frequency. In the normal state, the normalized noise power spectral density ${\mathit{S}}_{\mathit{n}}$(f) was observed to be several orders of magnitude greater than that of normal metals. Near the superconducting transition temperature, we observed a marked increase in ${\mathit{S}}_{\mathit{n}}$(f) with and without an external magnetic field. Moreover, in this region, we observed an unusual frequency dependence of the noise power spectral density on the external magnetic field.