Knowledge

3 条关联记录

10 条关联记录

9 条关联记录

2 条关联记录

7 条关联记录

Ruddlesden-Popper镍氧化物在块材高压和薄膜外延约束条件下均表现出超导电性，但高度依赖于样品质量、氧含量、缺陷和应力状态。本文提出，亚稳态RP晶格仅在Ni-O框架的局部约束变形处于一个有界的剪切应变窗口内时才进入超导态；该变形控制着八面体旋转、层间Ni-O-Ni键角以及Ni dz²与dx²-y²轨道间的耦合。这一剪切应力约束超导电性（SSCS）框架统一解释了此前观察到的压力阈值、可逆性、空间不均匀性、压力介质依赖性、薄膜-衬底敏感性以及可重复性难题。SSCS场景并不替代键角、键长、轨道占据、氧化学计量或载流子密度等传统因素的作用，而是指明这些因素协同稳定超导态所需的力学与对称性条件。镍氧化物超导体表现出的脆性与异质性并非外在复杂性，而是超导态本身的核心诊断特征。该视角为改善可重复性提供了具体实验路径，并将压缩块材、外延薄膜、化学替代样品及杂化RP结构中的物理机制统一在同一概念框架内。

The discovery of high-temperature superconductivity near 80 K in bilayer nickelate La3Ni2O7 under high pressures has renewed the exploration of superconducting nickelate in bulk materials. The extension of superconductivity in other nickelates in a broader family is also essential. Here, we report the experimental observation of superconducting signature in trilayer nickelate La4Ni3O10 under high pressures. By using a modified sol-gel method and post-annealing treatment under high oxygen pressure, we successfully obtained polycrystalline La4Ni3O10 samples with different transport behaviors at ambient pressure. Then we performed high-pressure electrical resistance measurements on these samples in a diamond-anvil-cell apparatus. Surprisingly, the signature of possible superconducting transition with a maximum transition temperature (T c) of about 20 K under high pressures is observed, as evidenced by a clear drop of resistance and the suppression of resistance drops under magnetic fields. Although the resistance drop is sample-dependent and relatively small, it appears in all of our measured samples. We argue that the observed superconducting signal is most likely to originate from the main phase of La4Ni3O10. Our findings will motivate the exploration of superconductivity in a broader family of nickelates and shed light on the understanding of the underlying mechanisms of high-T c superconductivity in nickelates.

Recently, the bilayer nickelate La3Ni2O7 has been discovered as a new superconductor with transition temperature Tc near 80 K under high pressure1–3. Despite extensive theoretical and experimental work to understand the nature of its superconductivity4–29, the requirement of extreme pressure restricts the use of many experimental probes and limits its application potential. Here we present signatures of superconductivity in La3Ni2O7 thin films at ambient pressure, facilitated by the application of epitaxial compressive strain. The onset Tc varies roughly from 26 to 42 K, with higher Tc values correlating with smaller in-plane lattice constants. We observed the co-existence of other Ruddlesden–Popper phases within the films and dependence of transport behaviour with ozone annealing, suggesting that the observed low zero resistance Tc of around 2 K can be attributed to stacking defects, grain boundaries and oxygen stoichiometry. This finding initiates numerous opportunities to stabilize and study superconductivity in bilayer nickelates at ambient pressure, and to facilitate the broad understanding of the ever-growing number of high temperature and unconventional superconductors in the transition metal oxides.

Signatures of superconductivity near 80 K in a nickelate under high pressure

研究人员将软点接触安德列夫反射谱技术集成到棕榈型立方压砧高压腔中，通过基底锚定与外部导线分线策略，在高达15 GPa的静水压下稳定构建多个点接触结。对单质超导体Nb的基准测量验证了方法的可靠性，得到零温超导能隙比2Δ(0)/k_B T_c≈3.3。进一步应用于kagome金属超导体CsCr3Sb5和双层镍酸盐超导体La2PrNi2O7，观测到与常规BCS超导体截然不同的尖锐零偏压电导峰，并系统研究了其随温度、磁场和压力的演化。分析表明，这些谱学特征与非常规超导电性及可能的d波配对对称性相符，为理解其配对机制提供了直接谱学证据。该工作成功搭建了连接宏观电输运和微观光谱探针的高压实验平台，为广泛探索压力诱导非常规超导体的配对对称性开辟了新途径。