Role of local duality invariance in axion electrodynamics of topological   insulators
  Advances in material technology and confluence of ideas from particle physics, quantum field theory and condensed matter physics have led to the discovery of new states of matter as well as new physical phenomena: one of them termed as topological insulator has attracted a great deal of attention recently. Speculations on the possibility of observing the most elusive objects like axions and monopoles in topological insulators have led to studies that emphasize the role of symmetry and universality. In this paper we argue that electric-magnetic duality could be of deep significance in this context. We develop a duality invariant theory of topological insulators and show that under appropriate conditions this theory reduces to the axion electrodynamics for static case, topological quantization is related with the multi-valuedness of the duality gauge potential, and modifies Faraday's law for dynamical axion that would change the dispersion relation of axionic polariton. A new effect dual to the dynamical axion field effect is predicted and its physical consequences are discussed. 
S. C. Tiwari
physics.gen-ph