We analyze the $s+is$ state that is proposed as a candidate superconducting state for strongly hole-doped ${\mathrm{Ba}}_{1-x}{\mathrm{K}}_x{\mathrm{Fe}}_2{\mathrm{As}}_2$. Such a state breaks time-reversal symmetry (TRS) but does not break any other discrete symmetry. We address the issue as to whether TRS breaking alone can generate spontaneous currents near impurity sites, which could be detected in, e.g., muon spin relaxation experiments. We argue that there are no spontaneous currents if only TRS is broken. However, supercurrents do emerge if the system is put under external strain and $C_4$ lattice rotation symmetry is externally broken.

• Received 24 December 2014
• Revised 21 March 2015

DOI:https://doi.org/10.1103/PhysRevB.91.161102