Erratum: Directional bistability and nonreciprocal lasing with cold atoms in a ring cavity (Physical Review Letters (2018) 121 (163603) DOI: 10.1103/PhysRevLett.121.163603)

he gain mechanism responsible for lasing was incorrectly identified as being due to Mollow scattering on the |F=2?|F'=2' transition (notation as in the original Letter). Subsequent experiments show that gain arises from Raman scattering between the |F=1 and |F=2 hyperfine ground states, driven by the MOT repump light [1]. The rest of the results and conclusions are unchanged.