La_{1-x}Sr_xNiO_2正常态中由电子不稳定性诱导的自发旋转对称性破缺
Spontaneous rotational symmetry breaking induced by electronic instability in the normal state of La_{1-x} Sr_{x} NiO_{2}
AI总结：
该研究结合角分辨电阻率测量与DFT+DMFT计算，发现无限层镍酸盐La_{1-x}Sr_xNiO_2在x=0.05和0.25附近存在由电子不稳定性诱导的自发旋转对称性破缺。
摘要：
自发旋转对称性破缺（RSB）是铜基和铁基高温超导体中的标志性现象，被认为与超导性密切相关，二者均源于不同自由度与竞争量子态之间的相互作用。理解RSB对于揭示非常规超导性的微观起源至关重要。尽管无限层镍酸盐（ILNs）与铜基超导体具有相似的晶体结构和相同的标称3d电子构型，但它们在费米面拓扑、电子能带特征和电荷序方面存在显著差异。这些区别使ILNs成为研究非常规超导体中RSB的理想平台。通过在较宽温度和掺杂范围内进行角分辨电阻率测量，我们在掺杂浓度x=0.05和0.25附近识别出显著的RSB信号。基于密度泛函理论与动力学平均场理论相结合计算得到的强关联电子结构，我们发现计算所得电子极化率在相应掺杂浓度处具有峰结构，表明存在驱动RSB的显著电子不稳定性。对电子极化率的详细分析表明，费米能级处的范霍夫奇点对0.05 Sr掺杂时的电子不稳定性有显著贡献。我们的发现揭示了电子关联、范霍夫奇点和费米面嵌套在RSB出现中的重要作用。本工作不仅深化了对ILNs中电子行为的理解，也为探索其他非常规超导体中的RSB提供了新思路和新方法。
英文摘要：
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.
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