Spin-charge-entangled Kondo effect induced by a side-coupled Majorana zero mode

We investigate Kondo physics in a quantum dot side coupled to a Majorana zero mode, where the Majorana coupling induces both spin and charge fluctuations that determine low-energy behavior. Using a wave-function-based Schrieffer-Wolff transformation combined with numerical renormalization group calculations, we discover an $S{U}_{L}(2)$ spin-charge-entangled Kondo state, in which conduction electrons screen the spin-charge-entangled degrees of freedom of the Majorana-quantum dot subsystem. We show that the parity degeneracy of this state gives rise to spin-resolved Andreev-normal boundary conditions, resulting in non-Fermi-liquid behavior. Density matrix renormalization group simulations directly resolve a hallmark of these boundary conditions---a subleading even-odd effect in the screening cloud. Our framework bridges strongly correlated and topological phenomena, and naturally extends to ${\mathbb{Z}}_{N}$ parafermions and $SU(N)$ Kondo systems.