Abstract
We studied the isotope, pressure, and doping effects on the pseudogap temperature by neutron spectroscopic experiments of the relaxation rate of crystal-field excitations in . We found clear evidence for the opening of a pseudogap at in the whole doping range. Furthermore, the effect of oxygen isotope substitution was found to produce an upward shift of , whereas the application of pressure on the optimally doped compound results in a downward shift of . The opposite effect of oxygen isotope substitution and pressure application indicates that electron-phonon induced effects contribute to the pseudogap formation. The temperature dependence of the relaxation data is consistent with a gap function of predominantly -wave symmetry.
4 More- Received 9 March 2006
DOI:https://doi.org/10.1103/PhysRevB.74.184520
©2006 American Physical Society