Interplane charge dynamics in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$

We present c-axis polarized optical spectrum ${\mathrm{\sigma }}_{\mathit{c}}$(ω) and out-of-plane Hall coefficient (${\mathit{R}}_{\mathit{H}}^{\mathit{c}}$) in the normal state of ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ as a function of doping. While ${\mathrm{\sigma }}_{\mathit{c}}$(ω) is dominated by a Drude-like peak at ω=0 and ${\mathit{R}}_{\mathit{H}}^{\mathit{c}}$ has finite negative values in the overdoped region, the low-energy ${\mathrm{\sigma }}_{\mathit{c}}$(ω) is severely suppressed and nearly ω independent, and ${\mathit{R}}_{\mathit{H}}^{\mathit{c}}$ is very small for underdoped compounds. The results provide evidence for different charge dynamics normal to the planes and clearly demonstrate how the charge dynamics changes with doping.