Charge-transfer excitations in the model superconductor HgBa(2)CuO(4+delta).
We report a Cu -edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa(2)CuO(4+delta) at optimal doping (T(c)=96.5 K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly dispersive (<0.5 eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a remnant charge-transfer gap deep in the superconducting phase. Quite generally, our results, which include additional data for the Mott insulator La(2)CuO(4), demonstrate the importance of exploring the incident photon-energy dependence of the RIXS cross section.
Lu
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Department of Applied Physics, Stanford University, Stanford, California 94305, USA.
Chabot-Couture
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G
Zhao
X
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Hancock
J N
JN
Kaneko
N
N
Vajk
O P
OP
Yu
G
G
Grenier
S
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Kim
Y J
YJ
Casa
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D
Gog
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T
Greven
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