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

Summary

This study reports the discovery of high-magnetic-field-stabilized reentrant superconductivity in (Sm,Eu,Ca,Sr)NiO₂ infinite-layer nickelate thin films. Through resistive and radio-frequency inductive measurements, in addition to the low-field superconducting state, another superconducting state characterized by a sharp resistivity drop was observed in the high-field region, with a transition temperature of approximately 9.6–11.7 K in low-T_c samples, while in high-T_c samples (up to 31.7 K) the low-field and high-field superconducting phases merge, and the upper critical field far exceeds the Pauli paramagnetic limit. The phase diagram can be accurately described by a Werthamer-Helfand-Hohenberg (WHH) model modified with an internal exchange field, indicating that this phenomenon originates from the Jaccarino-Peter compensation mechanism, where the internal exchange field generated by the Eu²⁺ magnetic moments counteracts the applied magnetic field. This finding realizes for the first time field-induced reentrant superconductivity in materials with relatively high superconducting transition temperatures, offering a new pathway toward developing superconducting magnets and devices capable of operating under magnetic fields of several tens of teslas.

Materials

• SECNO (Sm,Eu,Ca,Sr)NiO₂

Methods

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

Keywords

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

Highlights

• 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.

Conclusions

• 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.

Main claims

• High-field-stabilized reentrant superconductivity is observed in infinite-layer nickelate SECNO thin films with T_c up to 40 K.
  • Evidence: 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.
  • Evidence: 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

Workflow

• sample_preparation — Thin films of SECNO exhibit both low-field and high-field superconducting states.
  • Materials: (Sm_1-x-y-zEu_xCa_ySrz)NiO₂ (SECNO) thin films
  • Methods: pulsed laser deposition
  • Observations: films show low-field superconductivity and high-field reentrant phase
• measurement — High-field reentrant superconductivity is observed through resistive and inductive measurements.
  • Materials: SECNO thin films
  • Methods: four-probe resistance measurement; radio-frequency inductive measurement using proximity-detector tank circuit in pulsed magnetic fields
  • Observations: 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.
  • Materials: experimental data from resistive and inductive measurements
  • Methods: Werthamer-Helfand-Hohenberg (WHH) model modified with internal exchange field; Tinkham model for angular dependence
  • Observations: 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.
  • Materials: SECNO thin films
  • Methods: Jaccarino-Peter compensation mechanism
  • Observations: internal exchange field cancels applied field, reducing Pauli pair-breaking