Bosonic phases across the superconductor-insulator transition in infinite-layer samarium nickelate

摘要

该研究通过将无限层钐镍氧化物超导薄膜制备成空间周期性网络结构，调控库珀对的相位相干性，实现了超导-绝缘体相变。实验中观测到周期为h/2e的磁阻振荡，直接证明了镍氧化物中2e库珀对的存在。相变主要受增强的超导涨落驱动，且库珀对在整个相变过程中参与电荷输运。研究还发现了两种异常金属态：一种出现在有限磁场下，另一种在零磁场下即可出现；这两种态均可由玻色子激发表征，暗示涡旋在基态中的动态角色。该工作确立了镍氧化物作为研究库珀对相位相干性调控下丰富玻色子相的关键平台。

材料

• Sm₀.95-xEu_xCa₀.05NiO₂

方法

• PLD
• topotactic reduction
• RIE
• transport measurements

关键词

• superconductor insulator transition
• cooper pairs
• anomalous metal
• bosonic strange metal
• quantum oscillations

亮点

• First observation of h/2e quantum oscillations in nickelate superconductors, confirming Cooper pairing.
• Discovery of a bosonic strange metal state in a nanopatterned nickelate film, analogous to cuprate networks.
• Establishes nickelates as a platform for studying bosonic phases via phase coherence engineering.

结论

• Magnetoresistance oscillations with period h/2e provide direct evidence of 2e Cooper pairing in nickelates.
• The SIT is driven by enhanced superconducting fluctuations, with Cooper pairs involved in transport across the transition.
• Two types of anomalous metallic phases are observed: one at finite magnetic fields and one down to zero field, characterized by bosonic excitations.
• A bosonic strange metal state with linear temperature-dependent resistance is observed below the superconducting onset.

主要论断

• Magnetoresistance oscillations with period h/2e provide direct evidence of 2e Cooper pairing in nickelates
  • 证据: From abstract: 'Magnetoresistance oscillations with a periodicity of h/2e provide direct evidence of 2e Cooper pairing in nickelates'
• Two types of anomalous metallic phases observed: at finite field and at zero field, characterized by bosonic excitations
  • 证据: From abstract: 'we observe two types of anomalous metallic phases, emerging respectively at finite magnetic fields and down to zero magnetic field. They can be characterized by bosonic excitations, suggesting the dynamic roles of vortices in the ground states'

研究流程

• film_growth_and_reduction — High-quality infinite-layer nickelate films
  • 材料: Sm₀.95-xEu_xCa₀.05NiO₃; LaAlO₃ substrate
  • 方法: pulsed-laser deposition; topotactic reduction with CaH₂
  • 观察: superconducting Sm₀.95-xEu_xCa₀.05NiO₂ films
• nanopatterning — Periodic network structure with 50 nm holes
  • 材料: Sm₀.95-xEu_xCa₀.05NiO₂ film; AAO mask
  • 方法: reactive ion etching
  • 观察: honeycomb network patterns
• low_temperature_transport_measurements — h/2e oscillations prove Cooper pairing; anomalous metallic states observed
  • 材料: Nanopatterned film
  • 方法: four-probe resistivity; lock-in technique
  • 观察: resistance vs temperature and field; magnetoresistance oscillations