In a seminal work, Gozar et al. reported on the high-temperature interface superconductivity in bilayers of insulating La₂CuO₄ and metallic La_2−xSr_xCuO₄ (x=0.45). An interesting question to address is how general and robust this interface superconductivity is. In the past, the cuprate bilayers were grown in a unique atomic-layer molecular beam epitaxy system, with a Sr doping range of x≤0.47, and the atomically flat interface was thought to be indispensable. Here, we have fabricated bilayers of La₂CuO₄ and La_2−xSr_xCuO₄ by pulsed laser deposition. We have tried to extend the nominal doping range of Sr from the previous maximum of 0.47 to the present 1.70 (the nominal Sr content in the targets). X-ray diffraction result indicates that our La_2−xSr_xCuO₄ films with x≤0.60 have very high crystalline quality; but the film crystalline structure degrades gradually with further increasing x, and finally the structure is fully lost when x reaches 1.40 and higher. Although the film quality scatters dramatically, our experiments show that there exists superconductivity for bilayers in nearly the entire over-doped Sr range, except for a non-superconducting region at x∼0.80. These observations demonstrate that the interface superconductivity in copper oxides is very general and robust.

在一项开创性的工作中，Gozar等人。报道了绝缘La ₂ CuO ₄和金属La _{2− x} Sr _x CuO ₄（x = 0.45）双层中的高温界面超导性。需要解决的一个有趣问题是该界面超导性的通用性和鲁棒性。在过去，铜酸盐双层在一个独特的原子层分子束外延系统中生长，用的锶掺杂范围X ≤0.47，和原子级平坦界面被认为是不可缺少的。在这里，我们制作了La ₂ CuO ₄和La _{2− x} Sr _x的双层通过脉冲激光沉积生成CuO ₄。我们已尝试将Sr的标称掺杂范围从以前的最大值0.47扩展到目前的1.70（目标中的标称Sr含量）。X射线衍射结果表明，对La _{2- X}的Sr _X的CuO _4层膜与X ≤0.60具有非常高的结晶质量; 但随着x的增加，薄膜的晶体结构逐渐退化，最终当x达到1.40或更高时，该结构完全消失。尽管膜的质量有很大的分散，但我们的实验表明，在几乎整个超掺杂的Sr范围内，双层都有超导性，除了在X ~0.80。这些观察结果表明，氧化铜中的界面超导性非常普遍且稳定。