Is ${\mathbf{BaCr}}_2{\mathbf{As}}_2$ symmetrical to ${\mathbf{BaFe}}_2{\mathbf{As}}_2$ with respect to half $3d$ shell filling?

We have performed an angle-resolved photoemission spectroscopy study of ${\mathrm{BaCr}}_2{\mathrm{As}}_2$, which has the same crystal structure as ${\mathrm{BaFe}}_2{\mathrm{As}}_2$, a parent compound of Fe-based superconductors. We determine the Fermi surface of this material and its band dispersion over 5 eV of binding energy. Very moderate band renormalization (1.35) is observed for only two bands. We attribute this small renormalization to enhanced direct exchange as compared to Fe in ${\mathrm{BaFe}}_2{\mathrm{As}}_2$, and to a larger contribution of the $e_g$ orbitals in the composition of the bands forming the Fermi surface, leading to an effective valence count that is reduced by Fe $d$-As $p$ hybridization.

Figure 1

(a) FS of ${\mathrm{BaCr}}_2{\mathrm{As}}_2$ in the antiferromagnetic state calculated within the LDA at $k_z=0$. The blue square indicates the first Brillouin zone (1 Cr/unit-cell notation) boundaries. The black dashed arrows indicate the momentum path of the calculations in Fig. 2. (b) Same as (a) but for $k_z=\pi$. (c) ARPES intensity plot integrated within a 10 meV window centered at $E_F$, recorded at 20 K using 73 eV $\left(k_z\approx 0\right),s$-polarized photons. (d) Same as (c) but with 56 eV $\left(k_z\approx \pi \right)$ photons. (e) and (f) Same as (c) and (d), respectively, but for $p$-polarized photons. The blue and red arrows on the left side of panels (c) and (e) indicate the direction of the detector slit and of the light polarization, respectively, for the data of the corresponding row. None of the intensity plots have been symmetrized.

Figure 2

Orbital projections of our LDA calculations in the AFM state, along the momentum path indicated with dashed arrows in Fig. 1. The thickness of the lines is proportional to the corresponding orbital content. Cr1 and Cr2 refer to orbitals of Cr with majority and minority spins, respectively.

Figure 3

(a) ARPES intensity plot along the $\mathrm{\Gamma }$-M direction for $k_z\approx 0$ $(h\nu =73$ eV), recorded with the $s$ polarization configuration. LDA calculations are overlapped for comparison. The line in purple refers to the $\beta$ band. (b) Same as (a) but recorded with the $p$ polarization configuration. (c) Curvature intensity plot corresponding to the data in (a). (d) Curvature intensity plot corresponding to the data in (b). (e) EDCs corresponding to the data in (a). (f) EDCs corresponding to the data in (b). (g)–(l) Same as (a)–(f), but for $k_z\approx \pi$ $(h\nu =56$ eV). (m) Intensity plot of FS in the $k_y-k_z$ plane recorded with $s$-polarized light. The momentum positions of the ARPES cuts recorded at 56 and 73 eV are indicated by dashed lines.

Figure 4

(a) Near-$E_F$ zoom of the curvature intensity plot obtained with $s$ polarization at $k_z\approx 0$. Dashed lines in red and in purple represent unrenormalized LDA bands and LDA bands renormalized by a factor 1.35, respectively. (b) Same as (a) but recorded with $p$ polarization at $k_z\approx 0$. (c) Same as (a) but recorded with $s$ polarization at $k_z\approx \pi$. (d) Same as (a) but recorded with $p$ polarization at $k_z\approx \pi$.