ELECTRONIC-STRUCTURE AS A FUNCTION OF DOPING IN YBA2CU3OX(6.2-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-6.9) STUDIED BY ANGLE-RESOLVED PHOTOEMISSION

We report angle-resolved photoemission studies on YBa2Cu3Ox with oxygen stoichiometry varied in the range 6.2x6.9. The distinct 1-eV peak, observed with h=24 eV at the X(Y) point(s), shifts monotonically toward higher binding energies (as much as 0.20 eV) as oxygen stoichiometry is reduced from x=6.9 to 6.3. The direction and the magnitude of the shift are consistent with a simple rigid-band filling picture. However, another distinct peak observed at the X(Y) point(s), but with energy very close to EF, remains at nearly the same energy when the oxygen stoichiometry is varied from 6.9 to 6.4. This behavior is not consistent with a rigid-band picture. The intensities of the 1-eV peak and the peak at EF are significantly attenuated when the material becomes insulating. © 1995 The American Physical Society.