Spin dynamics and resonant inelastic x-ray scattering in chromium with commensurate spin-density wave order

Abstract

We theoretically investigate spin dynamics and L3-edge resonant inelastic X-ray scattering (RIXS) of Chromium with commensurate spin-density wave (SDW) order, based on a multi-band Hubbard model composed of 3d and 4s orbitals. Obtaining the ground state with the SDW mean-field approximation, we calculate the dynamical transverse and longitudinal spin susceptibility by using random-phase approximation. We find that a collective spin-wave excitation seen in inelastic neutron scattering hardly damps up to ∼0.6 eV. Above the energy, the excitation overlaps individual particlehole excitations as expected, leading to broad spectral weight. On the other hand, the collective spin-wave excitation in RIXS spectra has a tendency to be masked by large spectral weight coming from particle-hole excitations with various orbital channels. This is in contrast with inelastic neutron scattering, where only selected diagonal orbital channels contribute to the spectral weight. However, it may be possible to detect the spin-wave excitation in RIXS experiments in the future if resolution is high enough.

Soft striped magnetic fluctuations competing with superconductivity inFe1+xTe

“…[28] A strong zone boundary dampening has been reported in superconducting iron based variants [29], in cuprates and associated with the onset of the electronic pseudogap [30], and predicted to exist in Cr metal. [31] Our results however mark a clear difference between parent cuprates (and even cuprates close to the charged doped boundary of superconductivity) [32,33] and iron based systems as we do not see localized spin-waves which can be interpreted in terms of a localized Heisenberg model on a Mott insulating ground state.…”

Resonant inelastic X-ray scattering in strongly correlated electron systems

“…Comparing Fig. 4(a) and (a), we see that the off-diagonal contributions to I L are significant at high-energy region, resulting in relatively weak intensity of the diagonal contribution [15]. This indicates that L-edge RIXS in multi-orbital system may not necessarily a good tool to see magnon excitation corresponding to inelastic neutron scattering data.…”

“…In order to see off-diagonal orbital contributions to RIXS, we show in Fig. 4 the calculated RIXS spectra for antiferromagnetic Cr with commensurate spin order [15]. A mean-field approximation for the ground state and the random-phase approximation for the dynamical response function have been used in the calculation.…”

“…Nevertheless this material is a good example to investigate the effect of orbital degrees of freedom on L-edge RIXS [15]. We use the first-collision approximation where only the l = 0 component is take in the ultrafast core-hole lifetime expansion (11) to make clear the contribution from orbital to RIXS.…”

“…This has been discussed from theoretical viewpoints [14,15] by examining antiferromagnetic metallic systems such as the parent compound of iron-based superconductors.…”