Magnetochiral Kerr effect with application to the cuprates

Rotation of polarization of light on transmission and reflection at materials with time-reversal breaking (Faraday and Kerr effects, respectively) has been studied for over a hundred years. We add to such phenomena by studying the optical properties of magnetochiral states, which are states with loop currents such that there is finite Hall effect at zero applied magnetic field. Qualitatively new features arise in reflection and transmission in such a state. This state is shown to be induced in underdoped cuprates given their observed magnetoelectric loop-current order and certain lattice symmetries. These results explain the observation of Kerr effects with unusual properties and help further confirm the nature of the symmetry breaking in underdoped cuprates.