Orbital-selective electronic excitations in iron arsenides revealed by simulated nonresonant inelastic x-ray scattering

Nonresonant inelastic x-ray scattering (NIXS) is a possible tool to detect charge excitations in electron systems. In addition, multipole transitions at high-momentum-transfer regions open a new possibility to determine orbital-selective electronic excitations in multiorbital itinerant $3d$ electron systems. As a theoretical example, we choose the antiferromagnetic state of iron arsenides and demonstrate that the orbital-selective excitations are detectable by choosing appropriate momentum transfer in NIXS. We propose that both NIXS and resonant inelastic x-ray scattering are complementary to each other for fully understanding the nature of orbital excitations in multiorbital itinerant electron systems.

Figure 1

The coefficient ${\alpha }_{\mu \nu }\left(\mathit{q}\right)$ defined in Eq. (3) for the ${\mathrm{Fe}}^{2+}$ ion. (a) $\mathit{q}/\left(2\pi \right)=[H,0,0]$. (b) The orbital diagonal part of ${\alpha }_{\mu \mu }\left(\mathit{q}\right)$ along the $[H,0,L]$ direction. $H$ changes from 0 to $1/2$ for each value of $L$.

Figure 2

Calculated NIXS spectra for the antiferromagnetic phase of Ba122. (a) Along the $[0,0,0]\text{−}[1/2,0,0]$ direction. (b) Along the $[0,0,8]\text{−}[1/2,0,8]$ direction. $E_{\mathrm{r}}$ is the energy unit introduced to take into account the renormalization of the band.

Figure 3

The coefficient ${\alpha }_{\mu \nu }\left(\mathit{q}\right)$ defined in Eq. (3) for the ${\mathrm{Fe}}^{2+}$ ion. $\mathit{q}/2\pi$ is along $[H_0,H_0,8]\text{−}[H_0+H,H_0,8]$. For each $H_0,H$ changes from 0 to 1/2. Each panel corresponds to each orbital $\nu$.

Figure 4

Calculated NIXS spectra for the antiferromagnetic phase of Ba122 along the $[1,1,8]-[3/2,1,8]$ direction. $E_{\mathrm{r}}$ is the energy unit introduced to take into account the renormalization of the band.

Figure 5

The same as Fig. 4 but for the paramagnetic phase of Ba122.

Figure 6

The difference intensity of NIXS between the antiferromagnetic phase (Fig. 4) and the paramagnetic phase (Fig. 5).