Xu Xiaotao, He Xi, Bollinger Anthony T, Shi Xiaoyan, Božović Ivan
Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY 11973, USA.
Department of Physics, The University of Texas at Dallas, Richardson, TX 75080, USA.
Nanomaterials (Basel). 2023 Jul 29;13(15):2207. doi: 10.3390/nano13152207.
The fabrication of trilayer superconductor-insulator-superconductor (SIS) Josephson junctions with high-temperature superconductor (HTS) electrodes requires atomically perfect interfaces. Therefore, despite great interest and efforts, this remained a challenge for over three decades. Here, we report the discovery of a new family of metastable materials, LaSrZnO (LSZO), synthesized by atomic-layer-by-layer molecular beam epitaxy (ALL-MBE). We show that LSZO is insulating and epitaxially compatible with an HTS compound, LaSrCuO (LSCO). Since the "parent" compound LaZnO (LZO) is easier to grow, here we focus on this material as our insulating layer. Growing LZO at very low temperatures to reduce cation interdiffusion makes LSCO/LZO interfaces atomically sharp. We show that in LSCO/LZO/LSCO trilayers, the superconducting properties of the LSCO electrodes remain undiminished, unlike in previous attempts with insulator barriers made of other materials. This opens prospects to produce high-quality HTS tunnel junctions.
采用高温超导（HTS）电极制备三层超导-绝缘体-超导（SIS）约瑟夫森结需要原子级完美的界面。因此，尽管人们对此兴趣浓厚并付出了巨大努力，但三十多年来这一直是一项挑战。在此，我们报告通过逐层分子束外延（ALL-MBE）合成的一类新型亚稳材料LaSrZnO（LSZO）的发现。我们表明，LSZO是绝缘的，并且与HTS化合物LaSrCuO（LSCO）外延兼容。由于“母体”化合物LaZnO（LZO）更容易生长，在此我们将这种材料作为我们的绝缘层。在非常低的温度下生长LZO以减少阳离子相互扩散，使得LSCO/LZO界面在原子尺度上非常清晰。我们表明，在LSCO/LZO/LSCO三层结构中，LSCO电极的超导性能并未减弱，这与之前使用其他材料制成的绝缘势垒的尝试不同。这为生产高质量的HTS隧道结开辟了前景。
