Aichner Bernd, Keppert Sandra, Pedarnig Johannes D, Lang Wolfgang
Faculty of Physics, University of Vienna, 1090, Vienna, Austria.
Institute of Applied Physics, Johannes Kepler University Linz, 4040, Linz, Austria.
Sci Rep. 2025 Apr 7;15(1):11855. doi: 10.1038/s41598-025-95932-9.
Few-unit cell thick Bi[Formula: see text]Sr[Formula: see text]CaCu[Formula: see text]O[Formula: see text] (Bi-2212) layers have recently attracted much interest due to their extreme anisotropy and two-dimensional superconductivity, although they are typically susceptible to ambient conditions. In this study, we report on thin films approximately 13 unit cells thick that are stable in air, exhibit high anisotropy, and demonstrate extraordinarily high critical currents. By examining the superconducting transition under magnetic fields applied in both out-of-plane and in-plane orientations, we estimate key parameters such as pinning potentials, coherence lengths, London penetration depth, anisotropy factor, and the Ginzburg-Landau parameter. The volume pinning force is better described by a model incorporating an exponential decay term attributed to pronounced thermally-assisted flux flow. The Hall effect in the Bi-2212 films exhibits an extensive anomaly with a double sign change that may challenge existing theoretical explanations for this poorly understood phenomenon in copper-oxide superconductors.
尽管少单元胞厚的Bi₂Sr₂CaCu₂O₈（Bi - 2212）层通常对环境条件敏感，但由于其极端各向异性和二维超导性，最近引起了广泛关注。在本研究中，我们报道了约13个单元胞厚的薄膜，这些薄膜在空气中稳定，表现出高各向异性，并展示出极高的临界电流。通过研究在面外和面内取向施加磁场下的超导转变，我们估计了诸如钉扎势、相干长度、伦敦穿透深度、各向异性因子和金兹堡 - 朗道参数等关键参数。体积钉扎力用一个包含归因于明显热辅助磁通流的指数衰减项的模型能更好地描述。Bi - 2212薄膜中的霍尔效应表现出广泛的异常，有双重符号变化，这可能对现有的关于铜氧化物超导体中这种理解不足的现象的理论解释提出挑战。
