Dependence of the superconducting transition temperature on the type and number of (formula presented) layers in (formula presented)

The (Formula presented) layer dependence of the superconducting transition temperature (Formula presented) at ambient pressure on the intrinsic transition temperature (Formula presented) of the type-I (Formula presented) plane in which the copper atom has fivefold pyramid coordination of oxygen and the fourfold square coordinated type-II plane is studied in terms of the generalized Lawrence-Doniach theory. Calculations show that the increase of (Formula presented) with the number of (Formula presented) layers benefits from the difference of the intrinsic (Formula presented) of the two types of (Formula presented) layers and that interlayer coupling between the neighboring (Formula presented) layers can enhance (Formula presented) for the multilayer cuprates. The upper limit of (Formula presented) is predicted to be 146 K for the bilayer thallium-based series. We present an extended pressure-induced charge transfer model for layered cuprate superconductors, assuming that the charge distribution among the crystallographically inequivalent (Formula presented) layers is nonhomogeneous, which enables us to investigate the pressure effect on the intrinsic (Formula presented) The intrinsic (Formula presented) of the two types of (Formula presented) layers is predicted to behave with pressure in a paraboliclike manner. For the optimally doped single, double, and triple (Formula presented) sheets compounds, the saturation values of (Formula presented) of the type-I (Formula presented) plane of 91.1, 119.6, and 133.9 K are obtained when (Formula presented) 2.9, and 6.0 GPa, respectively. For the underdoped Tl-2234 compound with (Formula presented) K, the calculated (Formula presented) of 118.5 K is obtained at (Formula presented) GPa. Under the application of pressure, the intrinsic (Formula presented) of the type-II (Formula presented) plane in Tl-2234 increases strongly compared with a modest increase of (Formula presented) in Tl-2223, possibly resulting from its underdoped nature. We suggest that at low pressure the (Formula presented) is the intrinsic (Formula presented) of the type-I (Formula presented) plane, and at relatively high pressures the intrinsic effect of the type-II plane dominates. Our theoretical results are in agreement with experiments.