Quiet and Noisy Metastable Voltage States in High-Tc Superconductors

The interaction between the telegraph noise and background voltage fluctuations in the current induced dissipative state of high-Tc BiSrCaCuO thin films has been investigated. Experimental time records of the voltage drop across current biased thin film strips show markedly different background noise traces in the up and down telegraph states. Detailed analysis demonstrates that fluctuations around the telegraph voltage levels are due to a unique background noise process. The apparent quiet and noisy voltage states are due only to differences in the effective frequency bandwidth at which background noise is seen at distinct telegraph levels. Changes of the background noise variance ratio with changing bias current follow changes of the statistical average lifetimes of the random telegraph process.