摘要
研究显示，La2PrNi2O7-δ薄膜中的两步超导转变源于其颗粒超导性质，即两种不同临界温度的超导颗粒相通过约瑟夫森结网络共存耦合。通过脉冲激光沉积制备的薄膜在臭氧退火后，输运测量发现即使在30 K附近残余电阻极小的情况下，仍出现明显的次级低温转变，导致零电阻温度仅约10 K。磁电阻滞后现象及对弱磁场的敏感响应与颗粒超导体的有效场模型一致，排除了自旋玻璃相的可能性。结构表征表明，氧不均匀性和局部结构紊乱（如单层相插层）是产生两相分离的主要原因。该发现揭示了双层镍酸盐薄膜中复杂超导行为的微观机制，并强调改善氧均匀性是实现更高零电阻温度体超导的关键，为后续光谱学研究奠定基础。
材料
方法
关键词
- granular superconductivity
- two step transition
- josephson junction network
- oxygen inhomogeneity
亮点
- Magnetoresistance hysteresis and sensitivity to weak magnetic fields align with the effective field model of granular superconductors.
- The secondary low-temperature transition persists even when residual resistance is minimal near 30 K, resulting in a zero-resistance temperature of only about 10 K.
结论
- The two-step superconducting transition originates from granular superconductivity with two distinct superconducting grain phases coupled by Josephson junctions.
- Oxygen inhomogeneity and local structural disorder are the primary causes of the phase separation.
主要论断
- The two-step superconducting transition in La2PrNi2O7 thin films arises from granular superconductivity with two distinct superconducting grain phases coupled by Josephson junctions
- 证据: Resistivity shows two distinct transitions; magnetoresistance hysteresis consistent with effective field model of granular superconductors; STEM reveals oxygen inhomogeneity and stacking faults
研究流程
- Thin film growth and annealing — Structural disorder correlates with two-step transition
- 材料: La2PrNi2O7 thin films on SLAO
- 方法: Pulsed laser deposition (PLD); Ozone annealing
- 观察: XRD peaks, STEM images show monolayer intergrowths
- Transport measurements — Granular superconductivity with two superconducting grain phases
- 材料: PPMS system
- 方法: Four-probe resistivity; Magnetoresistance
- 观察: Two-step superconducting transition; Hysteretic magnetoresistance; Weak-field sensitivity