0 Se p 20 10 Magnetic impurities in the honeycomb Kitaev model

We study the effect of coupling magnetic impurities to the honeycomb lattice spin−1/2 Kitaev model in its spin liquid phase. We show that a spin-S impurity coupled to the Kitaev model is associated with an unusual Kondo effect with an intermediate coupling unstable fixed point Kc ∼ J/S separating topologically distinct sectors of the Kitaev model. We also show that the massless spinons in the spin liquid mediate an interaction of the form S iαS 2 jβ/R 3 ij between distant impurities unlike the usual dipolar RKKY interaction SiαSjα/R 3 ij noted in various 2D impurity problems with a pseudogapped density of states of the spin bath. Furthermore, this long-range interaction is possible only if the impurities (a) couple to more than one neighboring spin on the host lattice and (b) the impurity spin S 6= 1/2.