Spin, charge and pairing correlations in a bilayer Hubbard model with an incipient band*

Understanding the pairing mechanism responsible for high-temperature superconductivity is one of the primary goals of the condensed matter physics community. The bilayer Hubbard model provides a simple testbed, in which one can study unconventional pairing in a multi-band system. This model can be tuned through a Lifshitz transition, where one of the bands is pushed below the Fermi energy, similar to the situation in monolayer iron-selenide. Here we discuss dynamic cluster approximation (DCA) Quantum Monte Carlo (QMC) calculations of this model for different parameter regimes. In particular, we describe how its pairing correlations evolve as one of the bands becomes incipient, and how this behavior is linked to changes in the dynamical spin and charge fluctuations.