In a triclinic iron pnictide superconductor, a spin resonance precursor, Nernst signal, and NMR density-of-states reduction all point to preformed Cooper pairs persisting to T* = 45 K, above Tc = 30 K.
Universal relation between magnetic resonance and superconducting gap in unconventional superconductors
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abstract
Unconventional superconductors such as the high-transition temperature cuprates, heavy-fermion systems and iron arsenide-based compounds exhibit antiferromagnetic fluctuations that are dominated by a resonance, a collective spin-one excitation mode in the superconducting state. Here we demonstrate the existence of a universal linear relation, $Er \propto 2\Delta$, between the magnetic resonance energy (Er) and the superconducting pairing gap ($\Delta$), spanning two orders of magnitude in energy. This relation is valid for materials that range from being close to the Mott-insulating limit to being on the border of itinerant magnetism. Since the common excitonic picture of the resonance has not led to such universality, our observation suggests a much deeper connection between antiferromagnetic fluctuations and unconventional superconductivity.
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2025 1verdicts
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Preformed Cooper Pairs in a Triclinic Iron Pnictide Superconductor
In a triclinic iron pnictide superconductor, a spin resonance precursor, Nernst signal, and NMR density-of-states reduction all point to preformed Cooper pairs persisting to T* = 45 K, above Tc = 30 K.