PSEUDOGAP AND SUPERCONDUCTING GAP IN THE ELECTRONIC RAMAN-SPECTRA OF UNDERDOPED CUPRATES

Raman spectra of YBa2Cu3O7-x and Bi2Sr2(Ca0.62Y0.38)Cu2O8+delta with T -c congruent to 0.65T(c)(max) in the underdoped regime of the phase di agram are studied as a function of temperature and polarization. At B- 2g (xy) symmetry a reduction of spectral weight by 10% for frequencies less than 700 cm(-1) or 15k(B)T(c) is found below approximately 200 K . Below T-c, a superconducting gap opens up which closely resembles th at observed at higher doping levels. It is compatible with d(x)2(-y)2 pairing and its amplitude 2 Delta(0) can be estimated to be 8k(B)T(c).