Kink in the Dispersion of Layered Strontium Ruthenates

We present detailed energy dispersions near the Fermi level along the high symmetry line $\Gamma X$ on the monolayer and bilayer strontium ruthenates ${\mathrm{S}\mathrm{r}}_2{\mathrm{R}\mathrm{u}\mathrm{O}}_4$ and ${\mathrm{S}\mathrm{r}}_3{\mathrm{R}\mathrm{u}}_2{\mathrm{O}}_7$, determined by high-resolution angle-resolved photoemission spectroscopy. A kink in the dispersion is clearly shown for the both ruthenates. The energy position of the kink and the slope in the low-energy part near the Fermi level are almost identical between them, whereas the dispersion in the high-energy part varies, like the behavior of the kink for the cuprate superconductors.

Figure 1

The calculated energy bands crossing $E_F$ for the tetragonal structure of (a) ${\mathrm{S}\mathrm{r}}_2{\mathrm{R}\mathrm{u}\mathrm{O}}_4$ [28] and (b) ${\mathrm{S}\mathrm{r}}_3{\mathrm{R}\mathrm{u}}_2{\mathrm{O}}_7$ [16] along the high symmetry line $\Gamma X$.

Figure 2

(a) MDC’s, (b) intensity plot, and (c) experimental band dispersion relation of ${\mathrm{S}\mathrm{r}}_3{\mathrm{R}\mathrm{u}}_2{\mathrm{O}}_7$ along the high symmetry line $\Gamma X$.

Figure 3

(a) MDC’s and (b) intensity plot of ${\mathrm{S}\mathrm{r}}_2{\mathrm{R}\mathrm{u}\mathrm{O}}_4$ along the high symmetry line $\Gamma X$. (c) The MDC-derived dispersions (solid circles) together with the calculated band structure. The dispersion of spectral feature A of ${\mathrm{S}\mathrm{r}}_3{\mathrm{R}\mathrm{u}}_2{\mathrm{O}}_7$, which was shifted to the $\Gamma$ point by $0.05\Gamma X$ in order to align with the Fermi momentum of ${\mathrm{S}\mathrm{r}}_2{\mathrm{R}\mathrm{u}\mathrm{O}}_4$, is also shown in (c) (open circles).

Figure 4

(a) The same as in Fig. 2a, but in an expanded momentum from the $\Gamma$ point to the $0.5\Gamma X$ point. (b) MDC at $E_F$ in the high symmetry line $\Gamma X$ and the expanded view. (c) The MDC-derived dispersions (solid and open circles).