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Register a new userOrigin of the different electronic structure of Rh- and Ru-doped Sr2IrO4
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One way to induce insulator to metal transitions in the spin-orbit Mott insulator Sr2IrO4 is to substitute iridium with transition metals (Ru, Rh). However, this creates intriguing inhomogeneous metallic states, which cannot be described by a simple doping effect. We detail the electronic structure of the Ru-doped case with angle-resolved photoemission and show that, contrary to Rh, it cannot be connected to the undoped case by a rigid shift. We further identify bands below $E_F$ coexisting with the metallic ones that we assign to non-bonding Ir sites. We rationalize the differences between Rh and Ru by a different hybridization with oxygen, which mediates the coupling to Ir and sensitively affects the effective doping. We argue that the spin-orbit coupling does not control neither the charge transfer nor the transition threshold.
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We use resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge to study the effect of hole doping upon the Jeff=1/2 Mott-insulating state in Sr2IrO4, via Rh replacement of the Ir site. The spin-wave gap, associated with XY-type spin-exchange anisotropy, collapses with increasing Rh content, prior to the suppression of the Mott-insulating state and in contrast to electron doping via La substitution of the Sr site. At the same time, despite heavy damping, the d-d excitation spectra retain their overall amplitude and dispersion character. A careful study of the spin-wave spectrum reveals that deviations from the J1-J2-J3 Heisenberg used to model the pristine system disappear at intermediate doping levels. These findings are interpreted in terms of a modulation of Ir-Ir correlations due to the influence of Rh impurities upon nearby Ir wave functions, even as the single-band Jeff=1/2 model remains valid up to full carrier delocalization. They underline the importance of the transition metal site symmetry when doping pseudospin systems such as Sr2IrO4.
The solid solution between the ferromagnetic metal SrRuO$_3$ and the enhanced paramagnetic metal SrRhO$_3$ was recently reported [K. Yamaura et al., Phys. Rev. B 69 (2004) 024410], and an unexpected feature was found in the specific heat data at $x$=0.9 of SrRu$_{1-x}$Rh$_x$O$_3$. The feature was reinvestigated further by characterizing additional samples with various Ru concentrations in the vicinity of $x$=0.9. Specific heat and magnetic susceptibility data indicate that the feature reflects a peculiar magnetism of the doped perovskite, which appears only in the very narrow composition range 0.85$<$$x$$le$0.95.
We investigated the electronic structures of the two-dimensional layered perovskite Sr$_{2}$textit{M}O$_{4}$ (textit{M}=4textit{d} Ru, 4textit{d} Rh, and 5textit{d} Ir) using optical spectroscopy and polarization-dependent O 1textit{s} x-ray absorption spectroscopy. While the ground states of the series of compounds are rather different, their optical conductivity spectra $sigma(omega)$ exhibit similar interband transitions, indicative of the common electronic structures of the 4textit{d} and 5textit{d} layered oxides. The energy splittings between the two $e_{g}$ orbitals, $i.e.$, $d_{3z^{2}-r^{2}}$ and $d_{x^{2}-y^{2}}$, are about 2 eV, which is much larger than those in the pseudocubic and 3textit{d} layered perovskite oxides. The electronic properties of the Sr$_{2}$textit{M}O$_{4}$ compounds are discussed in terms of the crystal structure and the extended character of the 4textit{d} and 5textit{d} orbitals.
We investigated the electronic structures of the perovskite-type 4$d$ transition metal oxides Sr$M$O$_3$ ($M$ = Zr, Mo, Ru, and Rh) using their optical conductivity spectra $sigma (omega)$. The interband transitions in $sigma (omega)$ are assigned, and some important physical parameters, such as on-site Coulomb repulsion energy $U$, charge transfer energy $Delta_{pd}$, and crystal field splitting $10Dq$, are estimated. It is observed that $Delta _{pd}$ and 10$Dq$ decrease systematically with the increase in the atomic number of the 4$d$ transition metal. Compared to the case of 3$d$ transition metal oxides, the magnitudes of $Delta_{pd}$ and 10$Dq$ are larger, but those of $U$ are smaller. These behaviors can be explained by the more extended nature of the orbitals in the 4$d$ transition metal oxides.
The electronic structures of CeRhSn and CeRuSn are self-consistently calculated within density functional theory using the local spin density approximation for exchange and correlation. In agreement with experimental findings, the analyses of the electronic structures and of the chemical bonding properties point to the absence of magnetization within the mixed valent Rh based system while a finite magnetic moment is observed for trivalent cerium within the Ru-based stannide, which contains both trivalent and intermediate valent Ce.
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