Majorana fermion formulation of the two channel Kondo model

Abstract

We show that a Majorana fermion description of the two channel Kondo model can emerge quite naturally as a representation of the algebra associated with the spin currents in the two channels. Using this representation we derive an exact equivalent Hamiltonian for the two channel model expressed entirely in terms of Majorana fermions. The part of the Hamiltonian that is coupled to the impurity spin corresponds to the vector part of the $σ$-$τ$ model (compactified two channel model). Consequently all the thermodynamic properties associated with the impurity spin can be calculated from the $σ$-$τ$ model alone. The equivalent model can be used to confirm the interpretation of the many-body excitation spectrum of the low energy fixed point of the two-channel model as due to free Majorana fermions with appropriate boundary conditions.