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

Abstract

We present a study on the properties of superlattices made of ultrathin Sr2CuO4−δ layers sandwiched between La2CuO4 layers 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−δ slabs.

Advances in complex oxide quantum materials through new approaches to molecular beam epitaxy

“…Recent progress on MBE-grown cuprates as been exemplified by heterostructures involving La 2 CuO 4 [92] and YBa 2 Cu 3 O 7−x [93]. In heterostructures of Sr 2 CuO 4 and La 2 CuO 4 , STEM and EELS was used to obtain the spatial information on different CuO planes to help understand the localization of holes in superconducting heterostructures [94]. Further progress has also been made in the infinite-layer cuprates such as SrCuO 2 .…”

Bi‐Directional Growth of Thin Films: Unlocking Anisotropic Ferromagnetism and Superconductivity

“…[ 8 ] Molecular beam epitaxy (MBE) ushered in a new era by enabling the production of thin films with unprecedented qualities. [ 9–11 ] Notably, the integration of MBE growth for oxide materials led to the realization of record‐breaking physical properties, including high‐ T c superconductivity and colossal magnetoresistance. [ 12–16 ] However, a common characteristic shared by all epitaxial thin films, irrespective of their crystal structure and properties, is their reliance on a single growth direction.…”

Offcut Substrate-Induced Defect Trapping at Step Edges

“…We used specific offcut substrates, ensuring uniform terrace widths, and consequently reducing the distances between step edges resulting in a high density of step edges . Ozone-assisted molecular beam epitaxy (MBE) guided by reflection high-energy electron diffraction (RHEED) stands as the forefront technique, ensuring high quality complex oxide heterostructures. , This approach not only achieves exceptional film quality but also empowers precise control over the growth of individual unit cells. , Complex oxides have established themselves as record holders across an array of properties, including high- T C superconductivity, − colossal magnetoresistance, and multiferroicity, underscoring their exceptional versatility and performance …”