Premium
Raman Spectroscopy in YBa 2 Cu 3 O 6+x and Bi 2 Sr 2 (Ca x Y 1—x )Cu 2 O 8+δ : Pseudogap and Superconducting Gap
Author(s) -
Opel M.,
Nemetschek R.,
Venturini F.,
Hackl R.,
Erb A.,
Walker E.,
Berger H.,
Forró L.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199909)215:1<471::aid-pssb471>3.0.co;2-k
Subject(s) - pseudogap , superconductivity , condensed matter physics , fermi surface , doping , anisotropy , raman spectroscopy , symmetry breaking , materials science , raman scattering , spectroscopy , scattering , physics , cuprate , quantum mechanics
Abstract We present results of Raman‐scattering experiments in differently doped YBa 2 Cu 3 O 6+ x (Y‐123) and Bi 2 Sr 2 (Ca x Y 1— x )Cu 2 O 8+δ (Bi‐2212) single crystals. When reducing the doping level x the scattering intensity in B 1g symmetry increases while it decreases in the B 2g channel. This anisotropic behavior can be attributed to a qualitative change of the Fermi surface topology. At B 2g symmetry we find evidence of a pseudogap Δ* in the normal state below a characteristic temperature T * ≈ 180 K. In the superconducting state, the spectra obtained from overdoped samples show the well‐known pair‐breaking (2Δ) features in both B 1g and B 2g symmetries while in the underdoped regime pair‐breaking maxima can only be observed in the B 2g channel. The magnitude of the gap can be estimated to be approximately 8 kT c and is, from our experiments, different from Δ*.