Erratum: Kerr effect as evidence of gyrotropic order in the cuprates [Phys. Rev. B 87, 115116 (2013)]

Recent analysis has confirmed earlier general arguments that the Kerr response vanishes in any time-reversal invariant system which satisfies the Onsager relations. Thus, the widely cited relation between natural optical activity (gyrotropy) and the Kerr response, employed in our original paper, is incorrect. However, there is increasingly clear experimental evidence that, as argued in our paper, the onset of an observable Kerr signal in the cuprates reflects point-group symmetry rather than time-reversal symmetry breaking.