We present a study on the properties of superlattices
made of ultrathin
Sr2CuO4−δlayers sandwiched between
La2CuO4layers beyond the antiferromagnetic
insulating nature of the individual layers of choice. Using molecular
beam epitaxy, we synthesized these superlattices and observed superconductivity
and metallicity at the interfaces. We probed the hole distribution
to determine the discernible quantum states and found that the high-quality
epitaxy, combined with mapping the electronic fine structure by electron
energy-loss spectroscopy, allowed for the differentiation of insulating,
metallic, and superconducting layers at the atomic-column scale. Our
results demonstrate the possibility of exploring specific electronic
properties at the subnanometer scale and highlight the potential of
utilizing metastable Sr2CuO4−δslabs.