Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy.
CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy.
Phys Rev Lett. 2019 Feb 1;122(4):047002. doi: 10.1103/PhysRevLett.122.047002.
The study of superconductor-ferromagnet interfaces has generated great interest in the last decades, leading to the observation of spin-aligned triplet supercurrents and 0-π transitions in Josephson junctions where two superconductors are separated by an itinerant ferromagnet. Recently, spin-filter Josephson junctions with ferromagnetic barriers have shown unique transport properties, when compared to standard metallic ferromagnetic junctions, due to the intrinsically nondissipative nature of the tunneling process. Here we present the first extensive characterization of spin polarized Josephson junctions down to 0.3 K, and the first evidence of an incomplete 0-π transition in highly spin polarized tunnel ferromagnetic junctions. Experimental data are consistent with a progressive enhancement of the magnetic activity with the increase of the barrier thickness, as neatly captured by the simplest theoretical approach including a nonuniform exchange field. For very long junctions, unconventional magnetic activity of the barrier points to the presence of spin-triplet correlations.
在过去的几十年里，超导体-铁磁体界面的研究引起了极大的兴趣，导致在约瑟夫森结中观察到自旋对准的三线超导电流和 0-π 转变，其中两个超导体由巡游铁磁体隔开。最近，与标准金属铁磁结相比，具有铁磁势垒的自旋过滤约瑟夫森结由于隧道过程的固有非耗散性质，显示出独特的传输特性。在这里，我们首次对低至 0.3 K 的自旋极化约瑟夫森结进行了广泛的特性描述，并首次在高度自旋极化隧道铁磁结中证明了不完全的 0-π 转变。实验数据与最简单的理论方法一致，该方法包括非均匀交换场，该方法很好地捕捉到了随着势垒厚度的增加而导致的磁活性的逐步增强。对于非常长的结，势垒的非常规磁活性表明存在自旋三重态相关性。
