R. Nemetschek et al., PSEUDOGAP AND SUPERCONDUCTING GAP IN THE ELECTRONIC RAMAN-SPECTRA OF UNDERDOPED CUPRATES, Physical review letters, 78(25), 1997, pp. 4837-4840
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).