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Charge Density Wave Modulation in Superconducting BaPbO$_3$/BaBiO$_3$ Superlattices

The isotropic, non-magnetic doped BaBiO$_3$ superconductors maintain some similarities to high-Tc cuprates, while also providing a cleaner system for isolating charge density wave (CDW) physics that commonly competes with superconductivity. Artificial layered superlattices offer the possibility of engineering the interaction between superconductivity and CDW. Here we stabilize a low temperature, fluctuating short range CDW order by using artificially layered epitaxial (BaPbO$_3$)$_{3m}$/(BaBiO$_3$)$_m$ (m = 1-10 unit cells) superlattices that is not present in the optimally doped BaPb$_{0.75}$Bi$_{0.25}$O$_3$ alloy with the same overall chemical formula. Charge transfer from BaBiO$_3$ to BaPbO$_3$ effectively dopes the former and suppresses the long range CDW, however as the short range CDW fluctuations strengthens at low temperatures charge appears to localize and superconductivity is weakened. The monolayer structural control demonstrated here provides compelling implications to access controllable, local density-wave orders absent in bulk alloys and manipulate phase competition in unconventional superconductors.