Quantum critical physics in a bilayer Hubbard model system tuned by quantum interference

We study a bilayer Hubbard model, with five orbitals per unit cell, and show that the competing tunneling pathways between the layers can produce nontrivial many-body quantum interference effects. Structural distortions allow to tune the quantum interference, leading to a quantum critical point of two-channel-Kondo-lattice type. We treat the infinite-coordination limit of the model within dynamical mean field theory (DMFT), using the numerical renormalization group (NRG) as the impurity solver to obtain a numerically-exact solution directly on the real-axis, at zero and finite temperature. The effective impurity model is a self-consistent version of the critical 5-orbital/2-channel system discovered recently in [PRL 133, 076501 (2024)]. Although Jahn-Teller type distortions or charge disproportionation will naturally relieve the frustration in real systems and destroy the critical point, non-Fermi liquid signatures are expected at finite temperatures.