Superconducting critical state of Bi₂Sr₂CaCu₂O₈: Two-dimensional effects at low temperatures

The critical current in the c direction of Bi₂Sr₂CaCu₂O₈ is shown to increase with temperature in low temperature ZFC measurements. The results are consistent with a loss of the c direction long range phase correlation, induced by the temperature dependent critical current flowing in the ab planes. As a result of this and the loss of the long range correlation induced by thermal disorder, the low temperature electrical resistance of the ZFC critical state is finite at low temperatures, becomes zero and is finite again at higher temperature.