Design and Differentiation of Quantum States at Subnanometer Scale in La₂CuO₄-Sr₂CuO_4- Superlattices

We present a study on the properties of superlatticesmade of ultrathinSr(2)CuO(4-delta) layers sandwiched betweenLa(2)CuO(4) layers beyond the antiferromagneticinsulating nature of the individual layers of choice. Using molecularbeam epitaxy, we synthesized these superlattices and observed superconductivityand metallicity at the interfaces. We probed the hole distributionto determine the discernible quantum states and found that the high-qualityepitaxy, combined with mapping the electronic fine structure by electronenergy-loss spectroscopy, allowed for the differentiation of insulating,metallic, and superconducting layers at the atomic-column scale. Ourresults demonstrate the possibility of exploring specific electronicproperties at the subnanometer scale and highlight the potential ofutilizing metastable Sr2CuO4-delta slabs.