Using the functional renormalization group we investigated possible superconductivity in doped ${\mathrm{Sr}}_2{\mathrm{IrO}}_4$. In the electron-doped case, a $d_{x^2-y^2}^{*}$-wave superconducting phase is found in a narrow doping region. The pairing is driven by spin fluctuations within the single conduction band. In contrast, for hole doping an $s_{\pm }^{*}$-wave phase is established, triggered by spin fluctuations within and across the two conduction bands. In all cases there are comparable singlet and triplet components in the pairing function. The Hund's rule coupling reduces (enhances) superconductivity for electron (hole) doping. Our results imply that hole doping is more promising to achieve a higher transition temperature. Experimental perspectives are discussed.

• Received 18 December 2013
• Revised 10 March 2014

DOI:https://doi.org/10.1103/PhysRevB.89.094518