Majorana-Klein Hybridization in Topological Superconductor Junctions

We present a powerful and general approach to describe the coupling of Majorana fermions to external leads, of interacting or noninteracting electrons. Our picture has the Klein factors of bosonization appearing as extra Majorana fermions hybridizing with the physical ones. We demonstrate the power of this approach, analyzing a highly nontrivial SO(M) Kondo problem arising in topological superconductors with M Majorana-lead couplings, allowing for arbitrary M and for conduction electron interactions. Mapping the problem on a quantum Brownian motion model we find robust non-Fermi liquid behavior, even for Fermi liquid leads, and a quantum phase transition between insulating and Kondo regimes when the leads form Luttinger liquids. In particular, for M = 4 we find a stable realization of the two-channel Kondo fixed point. Obtaining the linear conductance at low temperatures, we predict transport signatures of this Majorana-Kondo-Luttinger physics.