Bose-Einstein to BCS Crossover Picture for High-T_c Cuprates

Combining (1) the universal correlations between $T_{c}$ and $n_{s}/m^{*}$ (superconducting carrier density / effective mass) and (2) the pseudo-gap behavior in the underdoped region, we obtain a picture to describe superconductivity in cuprate systems in evolution from Bose-Einstein to BCS condensation. Overdoped and Zn-substituted cuprate systems show signatures of reduced superfluid density in a microscopic phase separation. Scaling of $T_{c}$ to the superfluid volume density $n_{s}$ in all these cases indicate importance of Bose condensation.