Evidence for quasi-Fermi liquid behavior in one-dimensional interacting quantum systems

We present numerical evidence for a new paradigm in one-dimensional interacting fermion systems, whose phenomenology has traits of both Luttinger liquids and Fermi liquids. This new state, dubbed a quasi-Fermi liquid, was previously theoretically predicted to possess a discontinuity in its fermion occupation number at the Fermi energy while lacking the associated Landau quasiparticles. Such a state is realized in a one-dimensional spinless fermion Hamiltonian by fine-tuning the interactions to a regime where they become irrelevant in the renormalization group sense. We show, using uniform infinite matrix products states and finite-entanglement scaling analysis, that the system's ground state has a Luttinger parameter K = 1 and a discontinuous jump in the fermion occupation number. We support the characterization with calculations of the photoemission spectra. These results indicate that the quasi-Fermi liquid paradigm can be realized beyond the low-energy perturbative realm.