Understanding the bulk electronic structure of ${\mathrm{Ca}}_{1-x}{\mathrm{Sr}}_x\mathrm{V}{\mathrm{O}}_3$

We investigate the electronic structure of ${\mathrm{Ca}}_{1-x}{\mathrm{Sr}}_x\mathrm{V}{\mathrm{O}}_3$ using careful state-of-the-art experiments and calculations. Photoemission spectra using synchrotron radiation reveal a hitherto unnoticed polarization dependence of the photoemission matrix elements for the surface component leading to a substantial suppression of its intensity. Bulk spectra extracted with the help of experimentally determined electron escape depth and estimated suppression of surface contributions resolve outstanding puzzles concerning the electronic structure in ${\mathrm{Ca}}_{1-x}{\mathrm{Sr}}_x\mathrm{V}{\mathrm{O}}_3$.

Figure 1

(Color online) V $2p_{3∕2}$ spectra of (a) $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ and (b) ${\mathrm{Ca}}_{0.3}{\mathrm{Sr}}_{0.7}\mathrm{V}{\mathrm{O}}_3$ at different photon energies. The 1486.6 and $1253.6\mathrm{eV}$ spectra of $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ and $1486.6\mathrm{eV}$ spectrum of ${\mathrm{Ca}}_{0.3}{\mathrm{Sr}}_{0.7}\mathrm{V}{\mathrm{O}}_3$ are adapted from Ref. 7. Solid lines show the fit using three Voigt functions (dashed lines) representing the contributions from ${\mathrm{V}}^{3+}$, ${\mathrm{V}}^{4+}$, and ${\mathrm{V}}^{5+}$ entities. (c) Estimated $\lambda ∕d$ vs $\sqrt{\mathrm{KE}}$. $\lambda ∕d$ at $\mathrm{KE}=16\mathrm{eV}$ is obtained from the valence band analysis (Refs. 7, 8). Dotted-dashed line shows the trend at low energies. The solid line represents the calculated escape depth using TPP2M relations (Ref. 16).

Figure 2

(Color online) (a) Schematic of the photoemission plane. (b) Valence-band spectra of $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ at $40.8\mathrm{eV}$ using laboratory and synchrotron sources. (c) $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ at $275\mathrm{eV}$, (d) $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ at $275\mathrm{eV}$, and (e) $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ at $800\mathrm{eV}$. The $800\mathrm{eV}$ spectral line shape from scraped (open circles) and fractured (solid circles) $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ surfaces are very similar. (f) V $2p_{3∕2}$ spectra using $800\mathrm{eV}$ photons.

Figure 3

(Color online) (a) Calculated V $3d$ PDOS at VO-terminated surface. (b) Extracted bulk spectral functions of $\mathrm{Sr}\mathrm{V}{\mathrm{O}}_3$ (solid circles) and $\mathrm{Ca}\mathrm{V}{\mathrm{O}}_3$ (open circles). (c) $\mathrm{LDA}+\mathrm{DMFT}$ results adapted from Ref. 12.