SO(5) critical point in a spin-flavor Kondo device: Bosonization and refermionization solution

We investigate a well-studied system of a quantum dot coupled to a Coulomb box and leads, realizing a spin-flavor Kondo model. It exhibits a recently discovered non-Fermi liquid (NFL) behavior with emergent SO(5) symmetry. Here, through a detailed bosonization and refermionization solution, we push forward our previous work and provide a consistent and complete description of the various exotic properties and phase diagram. A unique NFL phase emerges from the presence of an uncoupled Majorana fermion from the flavor sector, whereas Fermi liquid-like susceptibilities result from the gapping out of a pair of Majorana fermions from the spin and flavor sectors. Other properties, such as a scaling of the conductance, stability under channel or spin-symmetry breaking, and a reappearance of NFL behavior upon breaking the particle-hole symmetry, are all accounted for by a renormalization group treatment of the refermionized Majorana model.