We present results for the optical conductivity of ${\mathrm{Na}}_2{\mathrm{IrO}}_3$ within density functional theory by including spin-orbit and correlation effects as implemented in the generalized gradient approximation. We identify the various interband transitions and show that the underlying quasimolecular-orbital nature of the electronic structure in ${\mathrm{Na}}_2{\mathrm{IrO}}_3$ translates into distinct features in the optical conductivity. Most importantly, the parity of the quasimolecular orbitals appears to be the main factor in determining strong and weak optical transitions. We also present optical conductivity calculations for $\alpha -{\mathrm{Li}}_2{\mathrm{IrO}}_3$ and discuss the similarities and differences with ${\mathrm{Na}}_2{\mathrm{IrO}}_3$.

• Received 16 October 2014
• Revised 13 January 2015

DOI:https://doi.org/10.1103/PhysRevB.91.161101