Fluctuating diamagnetism in underdoped high-temperature superconductors - art. no. 014510

The fluctuation-induced diamagnetism of underdoped high-temperature superco nductors is studied in the framework of the Lawrence-Doniach model. By taki ng into account the fluctuations of the phase of the order parameter only, the latter reduces to a layered XY model describing a liquid of vortices th at can be either thermally excited or induced by the external magnetic held . The diamagnetic response is given by a current-current correlation functi on that is evaluated using the Coulomb-gas analogy. Our results are then ap plied to recent measurements of fluctuation diamagnetism in underdoped YBa2 Cu3O6.67. They make possible the understanding of both the observed anomalo us temperature dependence of the zero-field susceptibility and the two dist inct regimes appearing in the magnetic-field dependence of the magnetizatio n.