Evidence of redistribution of the itinerant holes belowTcinBa2

Electronic structure studies of the Bi2212 system by polarised X-ray absorption measurement

“…Thus the difference between the holes at LT and RT appears ~ 10-14%. This is in agreement with our O K XAS measurements where we have given evidence for the redistribution of itinerant holes [16] in the Bi2212 system. The present results are also in support of the IPES study of Wagener et al [18] where an increase in the 2p holes has been reported.…”

“…Our polarised XAS measurements at the O K edge on the different crystals have shown ~ 9-13% density of p~ holes and led us to conclude to the presence of a significant density of the p~ symmetry orbitals available for the doping holes [10,16]. We have shown the estimation of the p~ holes for the different crystals in Figs.…”

“…Results are shown for the unoccupied 3d electronic states of different symmetries in the superconducting as well as normal state. We also give O K XAS data on the crystals for which details have been reported elsewhere [16]. The temperature-dependent changes in the Cu L 3 XAS line shapes, reflected by an increase in the 3dg_L/3d 9 ratio while going from the normal to the superconducting state of the system, are discussed as an effect of redistribution of the itinerant holes due to structural changes taking place in the system.…”

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].…”

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

“…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.…”