Pseudo gap and its relation to anomalous features in underdoped Bi2212

We report detailed resonance Raman investigations of the pseudo gap and the anomalous modes observed in underdoped Bi2Sr2CaCu2O8+/-delta. We observed similarity in the resonance profiles of the B-1g 600 cm(-1) peak and the A( 1g) 630 cm(-1) phonon mode, which provides strong evidence for the origin o f the 600 cm(-1) feature to be in some part a vibrational mode. At low temp eratures we observed an increase in intensity in the feature and depletion in spectral weight. We attribute the origin of the anomalous feature to two independent components, vibrational and electronic, with coincidental over lapping. Copyright (C) 2001 John Wiley & Sons, Ltd.