Comparative study of correlation effects in $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ and $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$

We present parameter-free $\mathrm{LDA}+\mathrm{DMFT}$ (local density $\text{approximation}+\text{dynamical}$ mean field theory) results for the many-body spectra of cubic $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ and orthorhombic $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$. Both systems are found to be strongly correlated metals, but not on the verge of a metal-insulator transition. In spite of the considerably smaller $\mathrm{V}\mathrm{O}\mathrm{V}$ bonding angle in $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$, the $\mathrm{LDA}+\mathrm{DMFT}$ photoemission spectra of the two systems are very similar, their quasiparticle parts being almost identical. The calculated x-ray absorption spectra show more pronounced, albeit still small, differences. This is in contrast to earlier theoretical and experimental conclusions, but in agreement with recent bulk-sensitive photoemission and x-ray absorption experiments.

Figure 1

(Color online) $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$, an ideal cubic perovskite, with $\mathrm{V}\mathrm{O}\mathrm{V}$ angle $\theta =\angle 123=180°$; V: large ions, ${\mathrm{O}}_{\text{basal}}$: small bright ions, and ${\mathrm{O}}_{\text{apex}}$: small dark ions.

Figure 2

(Color online) $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$, an orthorhombically distorted perovskite, with $\mathrm{V}\mathrm{O}\mathrm{V}$ angles ${\theta }_{\mathit{\text{basal}}}\approx 161°$, ${\theta }_{\mathit{\text{plane}}}\approx 163°$; V: large ions, ${\mathrm{O}}_{\text{basal}}$: small bright ions, and ${\mathrm{O}}_{\text{apex}}$: small dark ions. The local $c$ axis, later used for the definition of the orbitals, is directed along the tilted $\mathrm{V}{\mathrm{O}}_{\text{apex}}$ direction.

Figure 3

DOS of $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ as calculated by LDA(LMTO). Upper panel: $\mathrm{V}\text{−}3d$ (full line) and $\mathrm{O}\text{−}2p$ (dashed line) DOS; lower panel: partial DOS of $\mathrm{V}\text{−}3d$$\left(e_g\right)$ (full line) and $\mathrm{V}\text{−}3d\left(e_g\right)$ (dashed line) orbitals. The Fermi level corresponds to $0\mathrm{eV}$.

Figure 4

DOS of $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ as calculated by LDA(LMTO). Upper panel: $\mathrm{V}\text{−}3d$ (full line) and $\mathrm{O}\text{−}2p$ (dashed line) DOS; lower panel: partial DOS of $\mathrm{V}\text{−}3d$$\left(e_g\right)$ (full line) and $\mathrm{V}\text{−}3d\left(e_g\right)$ (dashed line) orbitals. The Fermi level corresponds to $0\mathrm{eV}$.

Figure 5

(Color online) Comparison of the LDA DOS of the $\mathrm{V}\text{−}3d$ ($t_{2g}$) band for $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ (solid line) and $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ (dashed line). In $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ the degeneracy of the three $t_{2g}$ bands is lifted (see inset). The bandwidth $W_{\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3}=2.5\mathrm{eV}$ is only 4% smaller than $W_{\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3}=2.6\mathrm{eV}$ (partially reproduced Fig. 2 from Ref. 19).

Figure 6

$\mathrm{LDA}+\mathrm{DMFT}\left(\mathrm{QMC}\right)$ spectrum of $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ (right panel) and $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ (left panel) calculated at $T\approx 300\mathrm{K}$ (solid lines), $T\approx 700\mathrm{K}$ (dashed lines), and $T\approx 1100\mathrm{K}$ (dotted lines).

Figure 7

Comparison of the parameter-free $\mathrm{LDA}+\mathrm{DMFT}\left(\mathrm{QMC}\right)$ spectra of $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ (solid line) and $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ (dashed line) with experiments below and above the Fermi energy. Left panel: high-resolution PES for $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ (circles) and $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ (rectangles) (Ref. 18). Right panel: $1s$ XAS for $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ (diamonds) and ${\mathrm{Ca}}_{0.9}{\mathrm{Sr}}_{0.1}\mathrm{V}{\mathrm{O}}_3$ (triangles) (Ref. 21). Horizontal line: experimental subtraction of the background intensity.