Magnetic and Orbital Excitations in Sr$_3$CuIrO$_6$
ORAL
Abstract
We report resonant inelastic x-ray scattering studies of the one-dimensional Sr$_3$CuIrO$_6$ at the Ir L$_3$ edge, with $\Delta$E=40 meV. At high energies, we find peaks at 0.6 eV, 0.9 eV, 3 eV, 4 eV and 6 eV. These peaks are non-dispersive, well-defined excitations. On the basis of quantum chemistry calculations, we are able to identify the first two as excitations within the $t_{2g}$ manifold and the next two as between the $t_{2g}$ and $e_g$ manifolds, together with charge transfer excitations from the O $2p$ to the Ir 5$d$. The 6 eV feature is another $t_{2g}$ - $e_g$ excitation. From these we are able to determine both the spin-orbit and non-cubic crystal field splittings. We find that they are of comparable strength. In addition, magnetic excitations are observed, corresponding to excitations of the $j_{1/2}$ isospin. We find these are highly dispersive along the chain direction with a bandwidth of 20 meV and a gap of 30 meV. These results allow a complete modeling of the spin and orbital degrees of freedom in this model compound and we conclude an atomic, spin-orbit coupled description works well.
*Work performed at BNL was supported by US DOE, Office of Science, DMSE under contract no. DE-AC02-98CH10886.
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