Spectral properties of strongly correlated multi-impurity models in the Kondo insulator regime: Emergent coherence, metallic surface states and quantum phase transitions

We employ a recently developed mapping of multi-impurity Anderson model onto an effective cluster to access the thermodynamics and the low-energy spectra in the Kondo insulator regime using Wilson's numerical renormalization group. Using a rigorous mathematical criteria on the maximal number of screening channels in a Kondo cluster, we show that the notion of a local Kondo screening fails in Kondo lattice systems: The spin singlet formation is mainly driven by the induced anti-ferromagnetic exchange between the correlated orbitals responsible for the AF part of the RKKY interaction. We address the question of a gapped local
spectral function employing extended Lieb Mattis theorem
For pristine Kondo lattice the theorem predicts the well established gaped the density of state at all site.
By adding a single stripe of uncorrelated sites to a conventional Kondo lattice model, however, we can show that a metallic surface state emerge which decays exponentially into the bulk. The extended Lieb-Mattis theorem confirms the finite density of states at the Fermi energy found in the NRG and in recent auxiliary field QMC spectra. Emerging quantum phase transitions in Kondo hole problems are addressed as well as their local spectral properties.

literature: Fabian Eickhoff, Frithjof B. Anders,
Phys. Rev. B 102, 205132 (2020)
Phys. Rev. B 104, 045115 (2021)
arXiv:2107.12777