Zero-field current-voltage characteristics in high-temperature superconductors

Zero-field current-voltage (I-V) data from a variety of samples of various high-temperature superconductors are re-analyzed to test the recently proposed current-temperature (I-T) phase diagram [S.W. Pierson, Phys. Rev. Lett. 74 (1995) 2359]. It is found that the I-V curves are well-described by this phase diagram. Furthermore, because the slopes of the various phase lines can be related to the effective interlayer coupling, it is shown that the I-T phase diagram provides a convenient framework in which to characterize samples. We discuss how the structure of the I-T phase diagram can be further tested and how more can be learned about these materials by probing parts of the I-T phase space which most experiments have neglected. Finally, further details of the I-T phase space are discussed.