Kondo effect in a PT-symmetric non-Hermitian Hamiltonian

The combination of non-Hermitian physics and strong correlations can give rise to new effects in open quantum many-body systemswith balanced gain and loss. We propose a generalized Anderson impurity model that includes non-Hermitian hopping terms between an embedded quantum dot and two wires. These non-Hermitian hopping terms respect a parity-time (PT) symmetry. In the regime of a singly occupied localized state, we map the problem to a PT-symmetric Kondo model and study the effects of the interactions using a perturbative renormalization group approach. We find that the Kondo effect persists if the couplings are below a critical value that corresponds to an exceptional point of the non-Hermitian Kondo interaction. On the other hand, in the regime of spontaneously broken PT symmetry, the Kondo effect is suppressed and the low-energy properties are governed by a localmoment fixed point with vanishing conductance.