State Key Laboratory for Heavy Oil Processing, PetroChina Key Laboratory of Catalysis, China University of Petroleum, Qingdao 266580, China.
Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Sci Rep. 2016 Sep 6;6:32963. doi: 10.1038/srep32963.
Sn is a classical superconductor on the border between type I and type II with critical temperature of 3.7 K. We show that its critical parameters can be dramatically increased if it is brought in the form of loosely bound bundles of thin nanowires. The specific heat displays a pronounced double phase transition at 3.7 K and 5.5 K, which we attribute to the inner 'bulk' contribution of the nanowires and to the surface contribution, respectively. The latter is visible only because of the large volume fraction of the surface layer in relation to the bulk volume. The upper transition coincides with the onset of the resistive transition, while zero resistance is gradually approached below the lower transition. In contrast to the low critical field Hc = 0.03 T of Sn in its bulk form, a magnetic field of more than 3 T is required to fully restore the normal state.
Sn 是一种处于 I 型和 II 型之间的典型超导体，其临界温度为 3.7K。我们表明，如果将其制成松散结合的细纳米线束形式，其临界参数可以显著提高。比热在 3.7K 和 5.5K 处显示出明显的双相转变，我们将其归因于纳米线的内部“体”贡献和表面贡献，分别。后者仅因为表面层相对于体层的大体积分数而可见。上转变与电阻转变的开始相吻合，而在较低转变以下，零电阻逐渐接近。与 Sn 在其体形式下的低临界场 Hc=0.03T 相比，需要超过 3T 的磁场才能完全恢复正常状态。
