Bosonic Phases across the Superconductor-Insulator Transitions in Infinite-Layer Samarium Nickelate

摘要

Bosonic Phases across the Superconductor-Insulator Transitions in Infinite-Layer Samarium Nickelate

材料

本批次暂无数据。

方法

本批次暂无数据。

关键词

本批次暂无数据。

亮点

本批次暂无数据。

结论

本批次暂无数据。

主要论断

• Magnetoresistance oscillations with period h/2e provide direct evidence of 2e Cooper pairing in nickelate superconductors.
  • 证据: Figure 2: clear oscillations with period corresponding to one flux quantum per honeycomb lattice cell,oscillation amplitude independent of excitation current below 200 nA
• The superconductor-insulator transition is driven by enhanced superconducting fluctuations, with Cooper pairs persisting across the transition.
  • 证据: T_c onset decreases only mildly from ≈20 K to ≈15 K while sheet resistance increases 20-fold,MR oscillations with h/2e period persist in the insulating state (S₁ No.4),kinks in Rs(T) curves indicate Cooper pairing within islands
• Two types of anomalous metallic states are observed: one at finite magnetic fields and one at zero magnetic field, both exhibiting intrinsic resistance saturation.
  • 证据: Figure 3: resistance saturation under applied field (S₁ No.2),Figure 4: resistance saturation at zero field (S₁ No.3),saturation independent of excitation current and RC filters
• The anomalous metallic state at finite field is consistent with quantum creep of vortices.
  • 证据: Field-dependent resistance at 0.26 K fits quantum creep model over 0.5 T to 2 T,suppression of Hall signal at low temperatures

研究流程

• Sample preparation — Nanopatterning via RIE through AAO masks enhances superconducting fluctuations and drives a superconductor-insulator transition.
  • 材料: Sm₀.95−xEu_xCa₀.05NiO₂ films; (LaAlO₃)₀.3(Sr₂TaAlO₆)₀.7 substrates; AAO masks
  • 方法: pulsed laser deposition (PLD); topotactic reduction; AAO mask transfer; reactive ion etching (RIE)
  • 观察: pristine film superconducting with T_c onset ≈20 K and zero resistance ≈7.5K; increasing etching time increases disorder and suppresses superconductivity
• Transport measurement — Cooper pairs are involved in transport across the SIT, and bosonic phases (AM state, strange metal) emerge from phase fluctuations.
  • 方法: electrical transport measurements (Rs vs T, Rs vs H); magnetoresistance (MR) measurements
  • 观察: MR oscillations with period ≈0.23 T = h/2e per network unit cell; resistance saturation to finite values at low T (anomalous metallic states); linear Rs(T) over wide T range (bosonic strange metal)
• Data analysis and interpretation — Two types of anomalous metallic states are observed, attributed to quantum vortex creep (finite field) and Ohmic dissipation of phase fluctuations (zero field).
  • 方法: background subtraction of MR; coherence length estimation from oscillation amplitude; quantum creep model fitting
  • 观察: phase coherence length ≈65 nm below 0.5K; oscillation amplitude inconsistent with Little-Parks effect, consistent with JJA; field-dependent resistance fits quantum creep model