Oxygen on-site Coulomb energy in Pr 1.3 − x La 0.7 Ce x CuO 4 and Bi 2 Sr 2 CaCu 2 O 8 + δ and its relation with Heisenberg exchange
Résumé
We study the electronic structure of electron-doped Pr 1.3−x La 0.7 Ce x CuO 4 (PLCCO; T c = 27 K, x = 0.1) and hole-doped Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212; T c = 90 K) cuprate superconductors using x-ray absorption spectroscopy and resonant photoemission spectroscopy (Res-PES). From Res-PES across the O K-edge and Cu Ledge , we identify the O 2p and Cu 3d partial density of states (PDOS) and their correlation satellites, which originate in two-hole Auger final states. Using the Cini-Sawatzky method, analysis of the experimental O 2p PDOS shows an oxygen on-site Coulomb energy for PLCCO to be U p = 3.3 ± 0.5 eV, and for Bi2212, U p = 5.6 ± 0.5 eV, while the copper on-site Coulomb correlation energy is U d = 6.5 ± 0.5 eV for Bi2212. The expression for the Heisenberg exchange interaction J in terms of the electronic parameters U d , U p , charge-transfer energy , and Cu-O hopping t pd obtained from a simple Cu 2 O cluster model is used to carry out an optimization analysis consistent with J known from scattering experiments. The analysis also provides the effective one-band on-site Coulomb correlation energy Ũ and the effective hopping t. PLCCO and Bi2212 are shown to exhibit very similar values of Ũ /t ∼ 9-10, confirming the strongly correlated nature of the singlet ground state in the effective one-band model for both materials.
Domaines
Matière Condensée [cond-mat]
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