Unusually high critical current of clean P-doped BaFe2As2 single crystalline thin film
F. Kurth, C. Tarantini, V. Grinenko, J. Haenisch, J. Jaroszynski, E. Reich, Y. Mori, A. Sakagami, T. Kawaguchi, J. Engelmann, L. Schultz, B. Holzapfel, H. Ikuta, R. Huehne, K. Iida
采用分子束外延技术在MgO（001）衬底上制备了微结构清洁的等离子P掺杂BaFe_2As_2（Ba-122）单晶薄膜。这些薄膜显示出超过30 K的超导转变温度（Tc），尽管P含量为约0.22，这低于单晶的最佳温度（即，0.33）。在此掺杂水平下的增强的Tc归因于面内拉伸应变。应变膜在4.2 K下具有超过6 MA/cm 2的高传输自场临界电流密度（Jc），这是Fe基超导体（FeSC）中最高的。对于H，在m0 H = 35 T时，场内Jc超过0.1 MA/cm 2|| ab和m0 H = 18 T（对于H）||c，分别在4.2 K，尽管温和的上临界场相比，其他FeSC具有类似的Tc。结构调查显示，没有缺陷或取向不良的晶粒指向强钉扎中心。我们将这种意想不到的高Jc与在最佳Tc处的涡核能量的强烈增强相关联，所述涡核能量由面内应变和掺杂驱动。这些异常高的Jc使得P掺杂的Ba-122非常适合高场磁体应用。
英文摘要：
Microstructura lly clean, isov alently P-doped BaFe2As2 (Ba-122) single crystalline thin films have been prepared on MgO (001) substrates by molecular beam epitaxy. These films show a superconducting transition temperature (Tc) of over 30 K although P content is around 0.22, which is lower than the optimal one for single crystals (i.e., 0.33). The enhanced Tc at this doping level is attributed to the in-plane tensile strain. The strained film shows high transport self-field critical current densities (Jc) of over 6 MA/cm2 at 4.2 K, which are among the highest for Fe based superconductors (FeSCs). In-field Jc exceeds 0.1 MA/cm2 at m0H = 35 T for H||ab and m0H = 18 T for H||c at 4.2 K, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar Tc. Structural investigations reveal no defects or misoriented grains pointing to strong pinning centers. We relate this unexpected high Jc to a strong enhancement of the vortex core energy at optimal Tc, driven by in-plane strain and doping. These unusually high Jc make P-doped Ba-122 very favorable for high-field magnet applications.
Family of Unconventional Superconductivities in Crystalline Graphene
Massachusetts Institute of Technology（麻省理工学院）；University of Basel（巴塞尔大学）；Florida State University（佛罗里达州立大学）；University of Florida（佛罗里达大学）；National Institute for Materials Science（国立材料研究所）
