In underdoped high-TC superconducting copper oxides a pseudogap develops well above TC. Whether the pseudogap is a distinct phenomenon or the incoherent continuation of the superconducting gap above TC is one of the central questions in high- TC research. A direct and unambiguous observation of a single-particle gap tied to the superconducting transition as function of temperature is discovered in underdoped Bi2Sr2CaCu2O8+δ.
- W. S. Lee
- I. M. Vishik
- Z.-X. Shen
