Majorana fermion formulation of the two channel Kondo model

TL;DR

This paper introduces a Majorana fermion representation of the two-channel Kondo model, deriving an exact Hamiltonian and analyzing thermodynamic properties and excitation spectra using this novel formulation.

Contribution

It provides a natural Majorana fermion formulation of the two-channel Kondo model and derives an exact Hamiltonian expressed solely in terms of Majorana fermions.

Findings

Hamiltonian expressed entirely in Majorana fermions

Thermodynamic properties derived from the $\sigma$-$ au$ model

Excitation spectrum interpreted as free Majorana fermions

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 $\sigma$-$\tau$ model (compactified two channel model). Consequently all the thermodynamic properties associated with the impurity spin can be calculated from the $\sigma$-$\tau$ 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.