Figure 1

(a) XRD $\theta$-$2\theta$ spectra of (0.19/0.06)${}_{n=10}$. The main Bragg peaks of (0 0 8) and (0 0 10) and the superlattice satellite peaks are marked. (b) Energy dependence of SL reflections near Ce and Cu edges measured with resonant soft x-ray scattering for sample (0.19/0.06)${}_{n=10}$. Horizontal arrows (with $-3$, $-4$, $-5$, $-6$) point to positions of superlattice peaks predicted from XRD measurements. Peaks are clearly visible at Ce $M$${}_4$ and $M$${}_5$ edges around 910 and 890 eV, respectively, but not at the Cu $L$${}_3$ edge. Shorter period oscillations in the figure are fringes due to finite sample thickness. The soft x-ray energy limits the scattering momentum at high $L$.Reuse & Permissions

Figure 2

(a) The resistivity, $\rho (T)$, of single-phase LCCO with $x=0.06$, 0.11, and 0.19, and also the (0.19/0.06)${}_{n=10}$ SL. Note that $\rho (T)$ of $x=0.06$ is divided by a factor of 3. (Inset) The real part of ac susceptibility vs. temperature for single-phase LCCO with $x=0.11$ (red) and (0.19/0.06)${}_{n=10}$ (green). (b) $T_c$ of single-phase LCCO ($▵$), ($x$/0.06)${}_{n=10}$ SL’s ($\square$). (c) $T_c$ of single-phase PCCO ($▵$), SL’s with fixed OD $x=0.19$ ($\square$) and BL’s ($◯$). The BL data are obtained from the structure of 240 nm $x=0.12$ and 60 nm $x=0.19$. $T_c$ of single-phase PCCO with $x=0.19$ is $~$7.3 K. The top and bottom of the error bars correspond to $T_c^{\mathrm{onset}}$ and $T_{c0}$, respectively.Reuse & Permissions

Figure 3

(a) $I$-$V$ of LCCO SL (0.19/0.06)${}_{n=40}$ from 8 to 19.5 K. Critical currents were determined using a $1\times {10}^{-6}$ V criteria. [(b) and (c)] The critical current density $J_c$ versus $T$ and (1- $T/T_{c0})$ of LCCO SL’s (0.19/0.06)${}_n$ with $n=40,20,10,6,$ respectively. (Inset) The structure configurations for (0.19/0.06)${}_n$. (d) $J_c$ versus (1-$T/T_{c0})$ of LCCO single-phase $x=0.11$ (divided by a factor of 3) and SL’s ($x$/0.06)${}_{n=10}$ with $x=0.17$, 0.19, and 0.21.Reuse & Permissions

Figure 4

The $c$-axis lattice parameter dependence of $T_{c0}$ for LCCO single-phase films prepared by PLD ($\square$), molecular beam epitaxy ($▽$),[19] PLD with buffer layer BaTiO${}_3$($▵$),[20] and magnetron sputtering ($◂$),[26] and also for (0.19/0.06)${}_n$ SL’s with different $T_c$ ($◯$). The dashed line marks the optimal doping. UD and OD represent underdoped and overdoped single-phase LCCO, respectively.Reuse & Permissions