Nonlocal screening effect in Cu 4pσ-1s resonant X-ray emission spectra in Nd2CuO4

We theoretically study polarization and momentum-transfer dependence in Cu 4p(alpha)-1s resonant X-ray emission spectra (RXES) of Nd2CuO4 with exact diagonalization techniques, developing our previous report [T. Ide and A. Kotani, J. Phys. Sec. Jpn. 68 (1999) 3100]. We explain the experimental polarization and angular dependence of a charge-transfer excitation about 5.7 eV above the ground state. Comparing results calculated with single- and multi-Cu models, we confirm the essential contribution of the nonlocal screening effect in Cu 4p(sigma)-1s RXES, together with the configuration dependence of d-p hybridization. We predict considerable dependence of a CT excitation at about 2eV on momentum transfer along the CuO2 planes, and the 5.7eV excitation has less dependence.