[论文解读] Two superconducting components with different symmetries in Nd1-xSrxNiO2 films

Qiangqiang Gu, Li, Yueying+9 more|arXiv (Cornell University)|Jun 23, 2020

Physics of Superconductivity and Magnetism参考文献 30被引用 33

一句话总结

该研究在Nd1-xSrxNiO2薄膜中报道了单粒子隧穿谱，揭示了具有不同能隙对称性的两种截然不同的超导分量（d-wave样和全隙），以及偶尔混合的情况，暗示在镍酸盐超导体中对CuO2的比拟相似性。

ABSTRACT

The pairing mechanism in cuprates remains as one of the most challenging issues in the field of condensed matter physics. The unique 3d9 electron orbital of the Cu2+ ionic states in cuprates is supposed to be the major player for the occurrence of superconductivity. Recently, superconductivity at about 9-15 K was discovered in infinite layer thin films of nickelate Nd1-xSrxNiO2 (x=0.1-0.2) which is believed to have the similar 3d9 orbital electrons. The key issue concerned here is about the superconducting gap function. Here we report the first set data of single particle tunneling measurements on the superconducting nickelate thin films. We find predominantly two types of tunneling spectra, one shows a V-shape feature which can be fitted very well by a d-wave gap function with gap maximum of about 3.9 meV, another one exhibits a full gap of about 2.35 meV. Some spectra demonstrate mixed contributions of these two components. Our results suggest that the newly found Ni-based superconductors play as close analogs to cuprates, and thus demonstrate the commonality of unconventional superconductivity.

研究动机与目标

• 将Nd1-xSrxNiO2薄膜中的超导能隙结构作为镍酸盐对CuO2的类比进行研究。
• 确定隧穿谱是否显示多重能隙分量，以及这些分量与能隙对称性的关系。
• 通过与CuO2比较来评估镍酸盐超导体配对机制的含义。

提出的方法

• 对Nd1-xSrxNiO2薄膜（x = 0.1–0.2）进行单粒子隧穿光谱学。
• 将谱拟合到超导能隙模型以识别对称性特征（例如d-wave 与全隙）
• 从谱中提取能隙量值，注意到不同分量及混合贡献。

实验结果

研究问题

• RQ1 Nd1-xSrxNiO2薄膜是否显示具有不同对称性的多种超导能隙分量？
• RQ2 与每个分量相关的能隙量值是多少，以及它们与类CuO2的镍酸盐超导体相比如何？
• RQ3 是否有某些谱显示能隙分量的混合？这对这些薄膜中的配对意味着什么？

主要发现

• 两种主要的隧穿谱类型：一种是V形谱，与d-wave能隙的拟合良好，最大值约为 ~3.9 meV；另一种是全隙谱，约为 ~2.35 meV。
• 一些谱显示来自两种能隙分量的混合贡献。
• 结果支持在非传统超导性方面镍酸盐超导体与CuO2的密切类比。