  A topological Kondo insulator (TKI) is a strongly-correlated material, where
hybridization between the conduction electrons and localized f-electrons gives
rise to a crossover from a metallic behavior at high temperatures to a
topologically non-trivial insulating state at low temperatures. The existing
description of the TKIs is based on a slave-boson mean-field theory, which
neglects dynamic fluctuation phenomena. Here, we go beyond the mean-field
theory and investigate the role of Kondo fluctuations on the topological
surface states. We derive an effective theory of the Dirac surface states
coupled to fluctuations and show that the latter mediate strong repulsive
interactions between surface excitations. We show that these effects
renormalize the plasmon spectrum on the surface. We also argue that
Kondo-mediated interactions may drive a magnetic instability of the surface
spectrum.
