标题： 正常态下电子不稳定性引起的自发旋转对称性破缺在 La_{1-x} Sr_{x} NiO_{2}中 显示英文标题

标题： Spontaneous rotational symmetry breaking induced by electronic instability in the normal state of La_{1-x} Sr_{x} NiO_{2}

摘要： 自发的旋转对称性破缺（RSB），是铜氧化物和铁基高温超导体中的标志性现象，被认为与超conductivity密切相关，两者都源于不同自由度之间的相互作用和竞争的量子态。理解RSB对于揭示非常规超conductivity的微观起源至关重要。尽管无限层镍氧化物（ILNs）与铜氧化物具有相似的晶体结构和相同的名义3d电子构型，但在费米面拓扑、电子能带特征和电荷有序方面存在显著差异。这些差异使ILNs成为研究非常规超conductors中RSB的理想平台。通过在大温度和掺杂范围内进行角度分辨电阻率测量，我们在掺杂浓度x=0.05和0.25附近识别出明显的RSB特征。基于结合密度泛函理论和动力学平均场理论计算的强关联电子结构，我们发现计算出的电子磁化率在相应的掺杂浓度处具有峰结构，表明存在明显的电子不稳定性，这驱动了RSB。对电子磁化率的详细分析表明，费米能级附近的范霍夫奇点在0.05Sr掺杂时显著贡献于电子不稳定性。我们的研究结果揭示了电子关联、范霍夫奇点和费米面嵌套在RSB出现中的重要作用。我们的工作不仅加深了对ILNs中电子行为的理解，还为探索其他非常规超conductors中的RSB提供了新的思路和方法。 显示英文摘要

摘要： The spontaneous rotational symmetry breaking (RSB), a hallmark phenomenon in cuprate and iron-based high-temperature superconductors, is believed to intimately connected to superconductivity, both of which originate from interactions among different degrees of freedoms and competing quantum states. Understanding RSB is pivotal for unraveling the microscopic origin of unconventional superconductivity. Although infinite-layer nickelates (ILNs) share similar crystalline structure and the same nominal 3d-electron configurations with cuprates, they have significant differences in Fermi surface topology, electronic band characteristics, and charge order. These distinctions make ILNs an ideal platform for studying RSB in unconventional superconductors. Through angular-resolved resistivity measurements within a large temperature and doping range, we identify pronounced RSB signatures near doping concentrations x=0.05 and 0.25. Based on the strongly correlated electronic structures from combined density functional theory and dynamical mean field theory calculations, we find that the calculated electronic susceptibility has a peak structure at the corresponding doping concentration, indicating pronounced electronic instabilities which drive RSB. Detailed analysis of the electronic susceptibility demonstrates that the van Hove singularity at the Fermi level significantly contributes to the electronic instability at 0.05 Sr doping. Our findings reveal the important role of electronic correlation, Van Hove singularity, and Fermi surface nesting in the emergence of RSB. Our work not only deepens the understanding of electronic behavior in ILNs, but also provides new ideas and methods for exploring RSB in other unconventional superconductors.