Strong-coupling pseudogap in an exactly solvable model of a doped Mott insulator

We demonstrate a pseudogap in the spectral function of the metallic phase of an exactly solvable model, which may be viewed either as an extended version of the Hatsugai-Kohmoto model or as an ensemble of small Hubbard model clusters under twisted boundary conditions. The pseudogap exhibits a decreasing energy scale and onset temperature for increased hole-doping, closure at a critical hole doping around 15%-20%, absence upon electron-doping, asymmetry in the addition and removal spectra, and persistence in the limit of infinitely strong interactions. The mechanism of the pseudogap in this model is due to orthogonality between bare electron excitations and low-energy spin-3/2, charge-1e excitations.