[论文解读] Investigations of key issues on the reproducibility of high-Tc superconductivity emerging from compressed La3Ni2O7

Yazhou Zhou, Jing Guo+12 more|arXiv (Cornell University)|Nov 21, 2023

Rare-earth and actinide compounds被引用 18

一句话总结

本文研究了La3Ni2O7在压力下引发的超导性的重现性问题，显示出类丝状的超导性、其界面起源以及氧含量的作用。

ABSTRACT

Recently, the signatures of superconductivity near 80 K have been discovered in the single crystal of La3Ni2O7 under pressure, which makes it a new candidate of the high-temperature superconductors dominated by 3d transition elements after the cuprate and iron-pnictide superconductors. However, there are several critical questions that have been perplexing the scientific community. These questions include (1) what factors contribute to the inconsistent reproducibility of the experimental results? (2) what is the fundamental nature of pressure-induced superconductivity: bulk or non-bulk (filamentary-like)? (3) where does the superconducting phase locate within the sample if it is filamentary-like? (4) is the oxygen content important for developing and stabilizing its superconductivity? In this study, we employ comprehensive high-pressure techniques to address these crucial issues. Through our modulated ac susceptibility measurements, we are the first to find that the superconductivity in this nickelate is filamentary-like. Our scanning transmission electron microscopy (STEM) investigations suggest that the filamentary-like superconductivity most likely emerges at the interface between the La3Ni2O7 and La4Ni3O10 phases. By tuning the oxygen content on the polycrystalline La3Ni2O7, we also find that the oxygen content plays vital role for developing and stabilizing its superconductivity. The upper and lower bounds of the oxygen content are 7.35 and 6.89, respectively. Our results provide not only new insights into understanding the puzzling issues in this material, but also significant information for achieving a better understanding on the superconductivity of this material.

研究动机与目标

• 动员在压力下报道的 La3Ni2O7 的高-Tc 超导重现性问题。
• 确定超导性是体性还是丝状的，以及在样品中的定位位置。
• 检查结构和化学因素，特别是相界面和氧含量等对超导性的影响。
• 通过受控合成与加工为稳定化超导性提供指导。

提出的方法

• 对La3Ni2O7样品应用高压技术来探测超导性。
• 使用调制的AC磁化率来表征超导态。
• 进行扫描透射电子显微镜（STEM）以定位潜在的超导区域。
• 对多晶La3Ni2O7进行氧含量的调控与评估，以评估其对超导性的影响。
• 确定相界面，特别是在La3Ni2O7和La4Ni3O10之间，作为潜在的超导性部位。
• 确定与超导性相关的氧含量的上、下限（7.35 和 6.89）。

实验结果

研究问题

• RQ1 在压力下观测到的超导性是体性还是丝状的？
• RQ2 如果存在丝状超导性，它在样品中的定位在哪里？
• RQ3 哪些因素能够解释不同实验之间重现性不一致的问题？
• RQ4 氧含量如何影响超导性的形成与稳定？
• RQ5 相界面在本材料中促进超导性发挥的作用是什么？

主要发现

• 根据调制的AC磁化率测量，压缩的La3Ni2O7中的超导性是丝状的。
• STEM 表明丝状超导性最有可能出现在La3Ni2O7与La4Ni3O10相之间的界面。
• 氧含量在超导性的形成和稳定方面具有显著影响。
• 所探讨的与超导性相关的氧含量区间为上限7.35和下限6.89。
• 研究结果为解决重现性问题和推进该镍酸盐材料超导性的理解提供了见解。