Polarization-resolved Cu L3 -edge resonant inelastic x-ray scattering of orbital and spin excitations in NdBa2Cu3O7−<

Abstract

High resolution resonant inelastic x-ray scattering (RIXS) has proven particularly effective in the determination of crystal field and spin excitations in cuprates. Its strength lies in the large Cu L3 resonance and in the fact that the scattering cross section follows quite closely the single-ion model predictions, both in the insulating parent compounds and in the superconducting doped materials. However, the spectra become increasingly broader with (hole) doping, hence resolving and assigning spectral features has proven challenging even with the highest energy resolution experimentally achievable. Here we have overcome this limitation by measuring the complete polarization dependence of the RIXS spectra as function of momentum transfer and doping in thin films of NdBa2Cu3O 7−δ . Besides confirming the previous assignment of dd and spin excitations (magnon, bimagnon) in the antiferromagnetic insulating parent compound, we unequivocally single out the actual spin-flip contribution at all dopings. We also demonstrate that the softening of dd excitations is mainly attributed to the shift of the xy peak to lower energy loss. These results provide a definitive assessment of the RIXS spectra of cuprates and demonstrate that RIXS measurements with full polarization control are practically feasible and highly informative.

Resonant inelastic x-ray scattering study of vector chiral ordered kagome antiferromagnet

“…This lower symmetry makes it possible to have a non-zero spin-flip intensity in the π in -π out channel. Our theoretical finding of a nonzero signal in the non-cross polarization channel has been recently experimentally observed in thin films of NBCO by Fumagalli et al 55 .…”

Many-Body Physics of Single and Double Spin-Flip Excitations in NiO

“…Trying to experimentally distinguish the double-magnons from noninteracting bimagnons therefore seems inconceivable. Neither a variation of scattering geometry helps, for both are expected to weakly disperse in momentum space, nor a polarization analysis, since both are expected to be allowed for the non-spin-flip RIXS scattering channels [18,31,32]. A single-site full-multiplet calculation with an equivalent superexchange field as in NiO well reproduces also the low energy-transfer spin-flip excitations from the experiment [Fig.…”

Structural, Electronic and Magnetic Properties of a Few Nanometer-Thick Superconducting NdBa2Cu3O7 Films

“…The spectra in Figure 3 are characterized by a quasi-elastic line at zero energy loss, spin excitations around 0.3 eV [22], while the most intense excitations at around 1.5 eV are crystal-field (or dd) transitions [10,21,22]. The inset in the same figure shows that the contribution of the amorphous NdBa 2 Cu 3 O 7 protective layer to the RIXS signal is negligible.…”