Low-energy interband transition in the infrared response of the correlated metal ${\mathrm{SrVO}}_3$ in the ultraclean limit

We studied the low-energy electronic response of the prototypical correlated metal ${\mathrm{SrVO}}_3$ in the ultraclean and disordered limit using infrared spectroscopy and density functional theory plus dynamical mean field theory calculations ($\mathrm{DFT}+\mathrm{DMFT}$). A strong optical excitation at 70 meV is observed in the optical response of the ultraclean samples but is hidden by the low-energy Drude-like response from intraband excitations in the more disordered samples. $\mathrm{DFT}+\mathrm{DMFT}$ calculations reveal that this optical excitation originates from interband transitions between the bands split by orbital off-diagonal hopping, which has often been ignored in cubic systems, such as ${\mathrm{SrVO}}_3$. A memory function analysis of the optical data shows that this interband transition can lead to deviations of optical self-energy from the expected Fermi-liquid behavior. Our findings demonstrate that analysis schemes employed to extract many-body effects from optical spectra may be oversimplified to study the true electronic ground state and that improvements in material quality can guide efforts to refine theoretical approaches.

Figure 1

(a) Temperature-dependent dc resistivity $\rho \left(T\right)$ of ${\mathrm{SrVO}}_3$ films. (b) X-ray diffraction $2\theta \text{−}\omega$ scans taken around the 002 peaks of ${\mathrm{SrVO}}_3$ films and LSAT substrate.

Figure 2

The real part of optical conductivity ${\sigma }_1\left(\omega \right)$ for (a) ${\mathrm{SrVO}}_3$ films with $\mathrm{RRR}=130$ and (b) $\mathrm{RRR}=6$. Insets: the log-log plot of ${\sigma }_1\left(\omega \right)$; closed circles correspond to the values of the dc conductivities taken from the $\rho \left(T\right)$ in Fig. 1. The dashed lines represent the extrapolated ${\sigma }_1\left(\omega \right)$.

Figure 3

(a) Band structure of ${\mathrm{SrVO}}_3$ from the DFT calculations (solid line) and the spectral function from the $\mathrm{DFT}+\mathrm{DMFT}$ calculations (color-coded). (b) Optical conductivity extracted from the DFT band structure (black line) and the $\mathrm{DFT}+\mathrm{DMFT}$ calculations (orange line). (c) Wannier model band structures for the full Hamiltonian (black line) and without the orbital off-diagonal hopping (red line). Inset shows the zoomed-in band dispersion in the $\mathrm{\Gamma }\text{−}M$ direction.

Figure 4

(a) Real and (b) imaginary parts of the memory function of the ${\mathrm{SrVO}}_3$ film with $\mathrm{RRR}=130$. (c) Real and (d) imaginary parts of the memory function of the ${\mathrm{SrVO}}_3$ film with $\mathrm{RRR}=6$. Dashed lines in (a), (c) and (b), (d) represent the linear and the quadratic frequency dependences of the real and imaginary parts of the memory function at 6 K, respectively.

Figure 5

(a) Drude–Lorentz fitting results of ${\sigma }_1\left(\omega \right)$ of the SVO-130 sample at 6 K. (b) The real part and (c) the imaginary part of the memory function for the intraband response [$M_1^{\mathrm{intra}}\left(\omega \right)$ and $M_2^{\mathrm{intra}}\left(\omega \right)$] of the SVO-130 sample at 6 K.