Ab-plane tunneling spectroscopy of underdoped

We have measured the tunneling spectra of underdoped and slightly overdoped (Formula presented) single crystals in the ab plane at different temperatures, ranging from 4.2 K to above (Formula presented) Gaplike spectra have been observed at low temperatures in both underdoped and overdoped compounds. However, overdoped samples do not display any gaplike features at temperatures above (Formula presented) On the contrary, the underdoped samples do display gaplike features above (Formula presented) The tunneling spectra in the pseudogap state are broader, giving rise to a larger gap value as compared to the superconducting state gap.