Hidden orbital fluctuations in the solid solution ${\mathrm{Y}}_{1-x}{\mathrm{La}}_x\mathrm{Ti}{\mathrm{O}}_3$ $(x<0.2)$

The electronic properties of ${\mathrm{Y}}_{1-x}{\mathrm{La}}_x\mathrm{Ti}{\mathrm{O}}_3$ $(x<0.2)$ solid solution are described using the state-of-the-art $\mathrm{LDA}+\mathrm{DMFT}$ method. It is shown that both structural distortions and multiorbital electron interactions are key aspects towards orbital polarization. Our results for stoichiometric $\mathrm{Y}\mathrm{Ti}{\mathrm{O}}_3$ explain various correlated features seen in one- and two-particle spectra of the paramagnetic insulating state. We also clarify the evolution of this correlated electronic state in the limit of small $x$. In agreement with optical experiments, we show that substitution of La for Y strongly renormalizes the one-particle spectra due to large transfer of spectral weight upon small perturbations.

Figure 1

(Color online) The effect of interorbital Coulomb interaction $U^{\prime }$ on the orbital-resolved and total one-electron spectral functions of $\mathrm{Y}\mathrm{Ti}{\mathrm{O}}_3$ in the paramagnetic phase for $U=5\mathrm{eV}$. Notice the changes in the correlated $t_{2g}$ spectral functions compared to the LDA ones, demonstrating the effect of electron interactions. In this and in the following figures the Fermi energy is placed at zero frequency.

Figure 2

(Color online) Comparison of theoretical $\mathrm{LDA}+\mathrm{DMFT}$ results for the total one-electron spectral function in the paramagnetic insulating phase of $\mathrm{Y}\mathrm{Ti}{\mathrm{O}}_3$ with photoemission results taken from Ref. 7. Inset: Comparison between calculated optical conductivity with experimental data (a) and (b) taken, respectively, from Refs. 5, 6.

Figure 3

(Color online) Effect of La-disorder in ${\mathrm{Y}}_{1-x}{\mathrm{La}}_x\mathrm{Ti}{\mathrm{O}}_3$: orbital-resolved and total one electron spectral functions. Notice the large changes in the correlated DOS due to disorder.