[论文解读] Paramagnetically driven superconducting re-entrance in Eu-doped infinite layer nickelates

Lucia Varbaro, Lukas Korosec+12 more|arXiv (Cornell University)|Jan 27, 2026

Magnetic and transport properties of perovskites and related materials被引用 0

一句话总结

论文报告在Eu掺杂的NdNiO2薄膜中观察到场诱导的再入超导，并显示这是由Eu2+与Nd3+磁矩之间的极化竞争所致，得到霍尔效应建模和基于Gorkov的对偶对裂理论的支持。

ABSTRACT

The breakthrough discovery of superconductivity in infinite-layer nickelates, and subsequently in several superconducting nickelates with more complex layered structures, capped a search spanning more than two decades and opened an entirely new field of research. Significant efforts aim to increase the critical temperature, to determine the electronic structure of the system, the underlying pairing mechanism, and the similarities between this system and cuprates - Ni1+ in infinite-layer nickelates being isoelectronic to Cu2+ in high-Tc cuprates. Here, we explore the unique role of magnetic rare earth ions in superconducting Eu-doped NdNiO2. We show that the field-induced re-entrant superconductivity which we evidence in this compound is the result of a delicate balance between the competing effects of the Eu2+ and Nd3+ ions. Our analyses of the extraordinary Hall effect and modeling of the superconducting critical fields demonstrate that the influence of these ions on magneto-transport is only felt when they are polarized by a magnetic field.

研究动机与目标

• 研究磁性稀土离子（Eu2+ 与 Nd3+）如何影响Nd1−xEuxNiO2中的超导性。
• 确定是否存在接近Jaccarino-Peter机制的解释，用于场诱导的再入超导在Eu掺杂的镍酸盐中的情形。
• 在高磁场下表征磁传输（包括霍尔效应）和超导相边界。
• 建立一个定量模型，将稀土自旋极化与非凡霍尔效应及超导抑制/恢复联系起来。

提出的方法

• 通过射频磁控溅射生长Nd1−xEuxNiO2薄膜（x=0.3），并在原位用金属Al还原以实现无限层相。
• 在垂直和水平磁场下测量电阻，磁场强度高达30 T，以绘制Tc(B)并观测再入超导。
• 对非超导和超导样品进行霍尔效应测量，以提取R0(T)和额外霍尔分量。
• 将Rxy(B,T)建模为R0(T)B + c[xNd⟨Nd3+(B,T)⟩ + xEu⟨Eu2+(B,T)⟩]，对Eu2+ (J=7/2)与Nd3+ (J=9/2)使用布里龙函数。
• 使用Gorkov的对裂理论，计算Bc2(T)，总场Btot包含来自Eu2+与Nd3+的交换贡献。
• 拟合模型参数（扩散系数D、自旋轨道时间τSO、有有效质量m*、交换耦合Γ）以匹配实验Bc2(T)数据。

Figure 1: (a) High-resolution X-ray diffraction scan around the (002) reflection of an optimally doped Nd 0.7 Eu 0.3 NiO 2 film grown on LSAT. The scan reveals an intense film peak, and the pronounced finite-size oscillations, marked by arrows, indicate high crystalline quality and smooth interfaces

实验结果

研究问题

• RQ1 Eu掺杂NdNiO2中导致异常场诱导再入超导的原因是什么？
• RQ2 Eu2+与Nd3+磁矩分别以及共同如何影响磁传输与超导性？
• RQ3 是否可以将扩展到两种磁离子的Jaccarino-Peter–类似机制解释观测到的霍尔响应与Tc在磁场下的恢复？
• RQ4 包括来自稀土离子的自旋交换场在内的总有效场如何决定Bc2(T)相边界？

主要发现

• 在最佳掺杂的Nd0.7Eu0.3NiO2在LSAT基底上，中等磁场（约3 T）出现再入超导，并在至少30 T下持续存在。
• 霍尔效应数据表现出非线性且随温度变化的贡献，归因于Eu2+与Nd3+磁矩；一个双亚晶格模型能拟合Rxy(B,T)。
• 基于布里龙函数的Eu2+ (J=7/2)与Nd3+ (J=9/2)磁矩极化在磁场下部分抵消内部场，降低传导电子所感受到的内部场。
• 结合总场Btot包含交换项的Gorkov对裂理论能够重现两种磁场取向下观测到的Bc2(T)非线性特征。
• X射线磁圆二色性测量支持Eu与Nd的磁化随场的极化行为，与模型一致。
• Eu/Nd的磁性相互作用对于观察到的低温场诱导超导至关重要；同等条件下，较高Tc样品不出现再入现象。

Figure 2: (a) Resistivity versus temperature curves for an optimized Nd 0.7 Eu 0.3 NiO 2 film on LSAT under perpendicular magnetic fields ranging from 0 T to 3.5 T in the top panel and 4 to 12 T in the bottom one. A conventional suppression of the superconducting transition temperature $T_{c}$ is ob