Towards two-dimensional superconductivity in La$_{2-x}$Sr$_{x}$CuO$_{4}$ in a moderate magnetic field*

We report a novel aspect of the competition and coexistence between antiferromagnetism and superconductivity in the prototypical high-Tc cuprate La$_{2-x}$Sr$_{x}$CuO$_{4}$ (La214). With a modest magnetic field applied $H \parallel c$-axis, we monitored the infrared signature of pair tunneling between the CuO$_{2}$ planes and discovered the complete suppression of interlayer coupling in a series of La214 single crystals. We find that the in-plane superconducting properties remain largely intact, in spite of increased antiferromagnetism in the planes. Thus, our experiments show that an isolated CuO$_{2}$ plane is capable of maintaining high-Tc superconductivity. The theoretical framework for antiferromagnetic-driven interlayer decoupling is identified in the work of Berg, \emph{et. al.} [E. Berg, \emph{et. al.}, Phys. Rev. Lett. \textbf{99}, 127003 (2007) and Cond-mat arXiv:0810.1564].