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Preformed Cooper Pairs in Layered FeSe-Based Superconductors
1Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
In iron-based superconductors, electron pairing precedes phase coherence, revealing pseudogap behavior linked to superconducting fluctuations. This finding highlights strong phase fluctuations in 2D superconductors.
Area of Science:
- Condensed Matter Physics
- Quantum Materials
Background:
- Superconductivity involves electron pairing and phase coherence.
- In cuprates, pairing can occur above phase coherence.
- The behavior in FeSe films is debated.
Purpose of the Study:
- Investigate if electron pairing precedes phase coherence in FeSe films.
- Reveal pseudogap behavior and its relation to superconducting fluctuations.
Main Methods:
- Nuclear spin-lattice relaxation rate measurements.
- Knight shift measurements.
- Detection of diamagnetic signals and Nernst effect.
Main Results:
- Pseudogap behavior observed below ~60 K in FeSe-based superconductors.
- Weak diamagnetism and notable Nernst effect in the pseudogap regime.
- Evidence suggests pseudogap is due to superconducting fluctuations.
Conclusions:
- Electron pairing precedes long-range phase coherence in these 2D iron-based superconductors.
- Strong phase fluctuations are a key characteristic, similar to cuprates.
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