Pseudogap phase in high-Tc superconductors

We describe the approach of the superconducting state as a sequence of crossover phenomena. As the temperature is decreased, uncorrelated pairing of the electrons leads to the opening of a pseudogap at T*(F). Upon further lowering the temperature those electron pairs acquire well behaved itinerant features at T*(B), leading to partial Meissner screening and Drude-type behavior of the optical conductivity. Further decrease of the temperature leads to their condensation and superconductivity at T-e. The analysis is done on the basis of the boson-fermion model in the crossover regime between 2D and 3D.