Natural Orbitals Renormalization Group Approach to Kondo Problems

We proposed a new concept in the framework of natural orbitals so that we can generalize the quantum renormalization group procedure into general orbital space, namely natural orbitals renormalization group (NORG), which takes a polynomial rather than exponential computational cost in the number of electron bath sites. Thus, the NORG is naturally appropriate for studying a quantum cluster-impurity model as well as an impurity solver to dynamical mean field theory. By using the NORG, we have studied multi-impurity or multi-channel Kondo problems.