[논문 리뷰] Investigations of key issues on the reproducibility of high-Tc superconductivity emerging from compressed La3Ni2O7

Yazhou Zhou, Jing Guo외 12명|arXiv (Cornell University)|2023. 11. 21.

Rare-earth and actinide compounds인용 수 18

한 줄 요약

이 논문은 La3Ni2O7에서의 압력에 의한 초전도성 재현성 문제를 조사하여 필라멘터리와 같은 초전도성, 그 인터페이스 기원, 그리고 산소 함량의 역할을 보여준다.

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.

연구 동기 및 목표

• 고압에서 La3Ni2O7에서 보고된 고-Tc 초전도성의 재현성 문제를 동기로 삼는다.
• 초전도성이 벌크인지 필라멘터리인지, 샘플 내 어디에 국소화되는지 확인한다.
• 상호 작용 구조 및 화학적 요인, 특히 상 경계와 산소 함량이 초전도성에 미치는 영향을 조사한다.
• 제어된 합성과 가공을 통해 초전도성의 안정화를 위한 지침을 제공한다.

제안 방법

• La3Ni2O7 시료에 고압 기술을 적용하여 초전도를 탐색한다.
• 초전도 상태를 특징화하기 위해 변조된 AC 자성 측정을 사용한다.
• 가능한 초전도 영역을 찾기 위해 스캐닝 전자현미경(STEM)을 수행한다.
• 다양한 다결정 La3Ni2O7의 산소 콘텐츠를 조정하고 그것이 초전도성에 미치는 영향을 평가한다.
• La3Ni2O7와 La4Ni3O10 사이의 상 경계가 초전도성의 잠재적 위치로서의 역할을 식별한다.
• 초전도성과 관련된 산소 함량의 상한과 하한(7.35 및 6.89)을 결정한다.

실험 결과

연구 질문

• RQ1 Is the observed superconductivity under pressure bulk or filamentary-like?
• RQ2 Where in the sample does filamentary superconductivity localize if present?
• RQ3 What factors reconcile inconsistent reproducibility across experiments?
• RQ4 How does oxygen content influence the development and stabilization of superconductivity?
• RQ5 What is the role of phase interfaces in enabling superconductivity in this material?

주요 결과

• Superconductivity in compressed La3Ni2O7 is filamentary-like according to modulated AC susceptibility measurements.
• STEM suggests filamentary superconductivity most likely emerges at interfaces between La3Ni2O7 and La4Ni3O10 phases.
• Oxygen content significantly affects the development and stabilization of superconductivity.
• The explored oxygen content bounds for superconductivity are 7.35 (upper) and 6.89 (lower).
• Findings provide insight into addressing reproducibility issues and advancing understanding of superconductivity in this nickelate material.