  Superlattices of the repeated structure La(1.56)Sr(0.44)CuO(4)/La(2)CuO(4)
(LSCO-LCO), where none of the constituents is superconducting, show a
superconducting transition of T_c \simeq 25 K. In order to elucidate the nature
of the superconducting state we have performed a low-energy muSR study. By
applying a magnetic field parallel (Meissner state) and perpendicular (vortex
state) to the film planes, we could show that superconductivity is sheet like,
resulting in a very anisotropic superconducting state. This result is
consistent with a simple charge-transfer model, which takes into account the
layered structure and the difference in the chemical potential between LCO and
LSCO, as well as Sr interdiffusion. Using a pancake-vortex model we could
estimate a strict upper limit of the London penetration depth to 380 nm in
these superlattices. The temperature dependence of the muon depolarization rate
in field cooling experiments is very similar to what is observed in
intercalated BSCCO and suggests that vortex-vortex interaction is dominated by
electromagnetic coupling but negligible Josephson interaction.
