Spin chirality and nontrivial charge dynamics in frustrated Mott insulators: spontaneouscurrents and charge redistribution**The paper is based on an invited talk at the International Conference on Magnetism,Karlsruhe, 2009.

Abstract

The standard point of view is that at low energies Mott insulators exhibit only magneticproperties, while charge degrees of freedom are frozen out because electrons are localized.We demonstrate (Bulaevskii et al 2008 Phys. Rev. B 78 024402) that in general this is nottrue: for certain spin textures there exist quite nontrivial charge effects in the ground andlowest excited states. We show that in frustrated systems spontaneous orbitalcurrents may exist in the ground state, proportional to the scalar spin chirality.For other spin structures spontaneous charge redistribution may exist, so thatthe average charge at a site is different from 1. This can lead to the appearanceof dipole moments and possibly of the net spontaneous polarization. This is anovel, purely electronic mechanism of multiferroic behaviour. We also discusssome dynamic consequences, such as dipole-active ‘ESR’ transitions. Also, thepossibility of using chirality instead of spin in memory applications is briefly discussed.