Role of two-dimensional electronic state in superconductivity in La$_{2-x}$Sr$_{x}$CuO$_{4}$

We have measured out-of-plane resistivity $rho_c$ for La$_{2-x}$Sr$_{x}$CuO$_{4}$ under anisotropic pressure. c-axis compression, which decreases $rho_c$, reduces $T_{rm c}$ drastically, whereas c-axis extention, which increases $rho_c$, enhances $T_{rm c}$ from 38K at ambient pressure to 51.6K at 8GPa. We find that the variation of $T_{rm c}$ scales as a function of $rho_c$, and that the c-axis pressure coefficient is much stronger than the ab-axis one. These imply that $T_{rm c}$ depends primarily on the interlayer, rather than the in-plane, lattice parameter.