High-field-stabilized reentrant superconductivity in infinite-layer nickelate thin films

摘要

本研究在(Sm,Eu,Ca,Sr)NiO₂无限层镍酸盐薄膜中发现了高磁场稳定的重入超导电性。通过电阻和射频感应测量，在低场超导态外，于高场区域观察到另一个电阻急剧下降的超导态，其转变温度在低T_c样品中约9.6–11.7 K，高T_c样品（最高31.7 K）中则表现为低场与高场超导相融合，上临界磁场远超泡利顺磁极限。利用修正了内交换场的Werthamer-Helfand-Hohenberg（WHH）模型可精确描述相图，表明该现象源于Eu²⁺磁矩产生的内交换场抵消外加磁场的Jaccarino-Peter补偿机制。这项发现首次在具有较高超导转变温度的材料中实现场诱导重入超导，为开发可在数十特斯拉磁场下工作的超导磁体与器件提供了新路径。

材料

• SECNO (Sm、Eu、Ca、Sr)NiO₂

方法

• Resistive measurements
• Radio-frequency inductive measurements
• X-ray absorption spectroscopy

关键词

• reentrant superconductivity
• jaccarino peter effect
• field induced superconductivity
• pauli paramagnetic limit

亮点

• First realization of field-induced reentrant superconductivity in a material with significantly high T_c (up to 40 K).
• Demonstrates a pathway toward superconductors that can operate at tens of tesla for applications in ultra-high-field magnets.

结论

• High-magnetic-field-reentrant superconductivity is observed in infinite-layer nickelate SECNO thin films.
• Both low-field and high-field superconducting states are consistent with the Jaccarino-Peter compensation mechanism.
• Unusually large upper critical fields are observed well beyond the Pauli paramagnetic limit.

主要论断

• High-field-stabilized reentrant superconductivity is observed in infinite-layer nickelate SECNO thin films with T_c up to 40 K.
  • 证据: resistivity drops by several orders of magnitude at high fields,RF inductive measurements show diamagnetic shift at high fields comparable to low-field superconducting state,sharp resistivity drop at high fields in samples with low T_c (9.6–11.7 K)
• The reentrant superconductivity is explained by the Jaccarino-Peter compensation mechanism involving internal exchange field from Eu₂+ magnetic moments.
  • 证据: phase diagrams accurately described by WHH model modified with internal exchange field,X-ray absorption spectroscopy confirms 67% Eu₂+ configuration,anomalous Hall effect matches Brillouin function for Eu₂+,angular dependence follows Tinkham model for two-dimensional superconductor

研究流程

• sample_preparation — Thin films of SECNO exhibit both low-field and high-field superconducting states.
  • 材料: (Sm_1-x-y-zEu_xCa_ySrz)NiO₂ (SECNO) thin films
  • 方法: pulsed laser deposition
  • 观察: films show low-field superconductivity and high-field reentrant phase
• measurement — High-field reentrant superconductivity is observed through resistive and inductive measurements.
  • 材料: SECNO thin films
  • 方法: four-probe resistance measurement; radio-frequency inductive measurement using proximity-detector tank circuit in pulsed magnetic fields
  • 观察: sharp resistivity drop at low fields; broad resistivity minimum at high fields indicating reentrant superconductivity; diamagnetic shift in RF measurement at high fields comparable to low-field state
• analysis — Phase diagrams are accurately described by WHH model with internal exchange field from Eu₂+ moments.
  • 材料: experimental data from resistive and inductive measurements
  • 方法: Werthamer-Helfand-Hohenberg (WHH) model modified with internal exchange field; Tinkham model for angular dependence
  • 观察: phase diagrams show two distinct superconducting phases; low-field and high-field phases merge at higher T_c (up to 31.7 K); upper critical field far exceeds Pauli paramagnetic limit
• interpretation — Reentrant superconductivity arises from Jaccarino-Peter effect where internal exchange field compensates applied magnetic field.
  • 材料: SECNO thin films
  • 方法: Jaccarino-Peter compensation mechanism
  • 观察: internal exchange field cancels applied field, reducing Pauli pair-breaking