Out-of-plane orbital characters of intrinsic and doped holes inLa2−xSr

Spatially modulated 'Mottness' in La2-xBaxCuO4

“…RSXS measurements were performed on beam line X1B at the National Synchrotron Light Source, Brookhaven, using a 10-axis, ultrahigh-vacuumcompatible diffractometer. The sample was cooled with a He flow cryostat connected through Cu braids, providing a base temperature of 18 K. X-ray absorption spectra (XAS) were measured in situ in fluorescence yield mode at the O K and Cu L 3/2 edges and found to be consistent with previous studies 8 (see Figs 1,3a). We will denote reciprocal space with Miller indices (H,K,L), which represent a momentum transfer Q = (2π/a H,2π/b K,2π/c L) where a = b = 3.788Å, c = 13.23Å.…”

“…As the hole density increases, spectral weight is transferred from the UHB to the MCP as the number of sites opposing electron addition decreases 8,9,22 . In this letter we take the spectral weight in the MCP to be a measure of the local hole density and that in the UHB to be a measure of the 'Mottness' 10 , that is, the degree to which there is a functioning Hubbard U, the degree to which the system resembles a Mott insulator.…”

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.…”

“…Bulk-sensitive (about 2500Å probing depth) FY spectra were recorded using a high-sensitivity seven-element Ge array detector. To achieve complete polarization geometry and to eliminate optical path variations, an azimuthal rotation method was used which has been discussed elsewhere in detail [18].…”

“…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.…”