X-Ray Photoemission Spectroscopy of Nd_2-xCe_xCuO_4-y and La_2-xSr_xCuO₄

Abstract

Resonant inelastic x-ray scattering (RIXS) at the copper K absorption edge has been performed for heavily overdoped samples of La2−xSrxCuO4 with x = 0.25 and 0.30. We have observed the charge transfer and molecular-orbital excitations which exhibit resonances at incident energies of Ei = 8.992 and 8.998 keV, respectively. From a comparison with previous results on undoped and optimally-doped samples, we determine that the charge-transfer excitation energy increases monotonically as doping increases. In addition, the Ei-dependences of the RIXS spectral weight and absorption spectrum exhibit no clear peak at Ei = 8.998 keV in contrast to results in the underdoped samples. The low-energy (≤ 3 eV) continuum excitation intensity has been studied utilizing the high energy resolution of 0.13 eV (FWHM). A comparison of the RIXS profiles at (π 0) and (π π) indicates that the continuum intensity exists even at (π π) in the overdoped samples, whereas it has been reported only at (0 0) and (π 0) for the x = 0.17 sample. Furthermore, we also found an additional excitation on top of the continuum intensity at the (π π) and (π 0) positions.

Crossing the Gap fromp- ton-Type Doping: Nature of the States near the Chemical Potential inLa2Steeneken1, Tjeng2, Sawatzky3 et al. 2003Phys. Rev. Lett.314170View full textAdd to dashboardCite

“…Core level x-ray photoemission (XPS) was carried out in Groningen. [4,17]. We clearly observe that the 2p3d 9 ''satellites'' decrease in intensity with Ce doping, and that also new structures, labeled as 2p3d 10 , start to appear on the low binding energy side of the 2p3d 10 L ''main lines,'' with 2p denoting a 2p core hole.…”

Progress and perspectives on electron-doped cuprates

“…The first Cu K-edge x-ray absorption study from Tranquada et al (1989) concluded that 3d 10 states formed upon Ce substitution, however a number of other early studies gave conflicting results (Fujimori et al, 1990;Ishii et al, 1989;Nücker et al, 1989). Note that in general, most of these kind of spectroscopies suffer from a strong sensitivity to surface quality.…”

Surface and interface study on MBE-grownNd1.85Ce0.15CuO4Yamamoto1, Naito2, Sato3 1997Phys. Rev. B464190View full textAdd to dashboardCite

“…Second, accurate information on the surface and interface seems to be needed to build HTSC-based tunnel junctions, the attempts at which have been unsuccessful in spite of tremendous efforts since the discovery of HTSC's. 8 NCCO has been extensively investigated by photoemission spectroscopies 6,7,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] because its surface is relatively stable among cuprates and also because it belongs to a small family of n-type HTSC's. 28,29 A comparison of these with those in the p-type family should shed light on the superconducting mechanism of HTSC's.…”