Symmetry of the3d9ligand hole induced by doping inYBa2

OK-edge and CuL23-edge XANES study on the concentration and distribution of holes in the(Pb2/Karppinen1, Kotiranta2, Yamauchi3 et al. 2001Phys. Rev. B214170View full textAdd to dashboardCite

“…With an increasing degree of Ca substitution, a feature due to the formally trivalent copper in the CuO 2 plane appears on the high-energy side of the 932.0 eV peak. This high-energy shoulder at ϳ933 eV, reported for the first time for the CuBa 2 YCu 2 O 6ϩz phase as a consequence of oxygen doping, 27 has been interpreted as transitions from the Cu (2p 3/2 )3d 9 L ground states into the Cu (2p 3/2 )3d 10 L excited states, where L denotes a ligand hole in the O 2p orbital. With an increasing Casubstitution level, the 932.0 eV peak becomes increasingly asymmetric, indicating that the amount of formally trivalent copper continuously increases ͑Table I͒.…”

Polarized x-ray absorption spectroscopy study of the symmetry of unoccupied electronic states near the Fermi level in the system

“…A significant density of p z holes has also been established in YBa 2 Cu 3 O ≈7 [3,12] and in the La-Sr-Cu-O [18] system by such studies. There is variation in data from one system collected using the TY and FY techniques and from two different systems using the same technique.…”

“…The present data yield an intensity of about 2-4%. Next, the Cu L 3 WLs for E ⊥ c and E c for crystal B are resolved into two Gaussians (figure 3) of FWHM about 1.1 eV separated by about 1.2 eV which is of the order of the charge transfer energy ( ) in the Bi-2212 system. The lower-energy main component L 3 arises from the transition 3d 9 → 2p 3d 10 while the doping-induced satellite component L 3 arises from 3d 9 L → 2p3d 10 L. Given the larger experimental uncertainties, the 3d z 2 -to-3d x 2 −y 2 intensity ratios for the doping-induced satellite peak L 3 are estimated to be 3%.…”

“…High-energy spectroscopy techniques, especially polarized x-ray absorption measurements, have been widely used in probing the electronic states near the Fermi level in these rather complex materials [1,2]. In particular, a number of polarized x-ray absorption spectroscopy (XAS) and electron energy loss spectroscopy (EELS) studies have been made to obtain valuable information on the symmetry of unoccupied states in the normal state [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], and to understand the behaviour of holes in the superconducting state [19,20]. The Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) compound has attracted more attention because interpretation in the 1-2-3 system is more complicated due to presence of the two non-equivalent Cu sites and because the surfaces of 1-2-3 compounds are unstable at room temperature under UHV conditions.…”

Soft x-ray absorption and high-resolution powder x-ray diffraction study of superconducting Ca La1−Ba1.75−La0.25+Cu3O system

“…Instead, when oxygen doping increases from heavily underdoped y=6.4 (x=0) to optimum doped y=7.13 (x=0), the feature around 932.9 eV gains its weight, while the feature around 934.3 eV disappears. The shoulder at ~932.9 eV is associated to Cu 3d 9 L → Cu 2p3d 10 L transitions and its spectral weight is proportional to the hole number in the valence band [23,24,[30][31][32][33]. The peak at ~934.3 eV is present only in the spectra of the heavily underdoped samples (y=6.4, x=0 and y=6.4, x=0.3) and is ascribed to Cu 1+ states in the O(4)-Cu(1)-O(4) dumbbell [23][24][25][26].…”