Pairing and two-fluid physics in low-dimensional quantum systems
The present thesis deals mainly with the ground-state properties of quantum many-body systems of spinless fermions that display bound-state formation. We start by discussing the pairing phenomena induced by density-density interactions, showing that extending the range of the latter can lead to the observation of exotic Luttinger liquid phases with cluster granularity. We continue the study of pairing in a one-dimensional chain of spinless fermions where single-particle hopping competes with a correlated pair-hopping interaction. We unveil a novel transition from a weak-coupling Luttinger liquid phase to a paired Luttinger liquid phase, that occurs through an intervening phase where a liquid of isolated fermions coexists with a liquid of pairs without phase separation. We confi\u001Crm the stability of this novel coexistence phase against the addition of a weak nearest-neighbor density-density interaction, which is shown to induce instead phase separation between paired and unpaired fermions in the strong-coupling regime. Finally, we generalize the pair-hopping term to a generic multimer-hopping term, thereby proving the robustness of the coexistence phase as the generic transition scenario between a Luttinger liquid with single-particle granularity and one with molecular granularity. We conclude by showing that models of spinless fermions featuring pair-hopping can host quantum many-body scars, thus opening further routes towards the study of weak ergodicity breaking in isolated many-body quantum systems.
L. Mazza (co-directeur de thèse)
G. Roux (co-directeur de thèse)
P. Simone (co-directeur de thèse)
K. Le Hur