Spectroscopic evidence for preformed Cooper pairs in the pseudogap phase of cuprates

• Angle-resolved photoemission on underdoped La1.895Sr0.105CuO4 reveals that in the pseudogap phase, the dispersion has two branches located above and below the Fermi level with a minimum at the Fermi momentum. This is characteristic of the Bogoliubov dispersion in the superconducting state. We also observe that the superconducting and pseudogaps have the same d-wave form with the same amplitude. Our observations provide direct evidence for preformed Cooper pairs, implying that the pseudogap phase is a precursor to superconductivity.

Nyckelord

high-t-c

underdoped bi2212

normal-state

superconductors

gap

bi2sr2cacu2o8+delta

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