Laboratoire de Physique Théorique

de la Matière Condensée

Guillaume Roux (LPTMS, Université Paris Saclay)

Coexistence and phase separation of pairs and fermions in a one-dimensional model with pair-hopping

We consider a simple model of spinless fermions in which the kinetic energy competes with a pair-hopping term. We show by means of numerical calculations that there exists a phase in which part of the fermions are paired while the others remain unpaired. These elementary components makes two mixed Luttinger liquids, one for pairs and one for fermions. A simple two-fluid model accounts remarkably well for the observed numerical data. Adding nearest-neighbour interaction leads to a rich phase diagram in which we observe a regime in which the two previous Luttinger liquids get phase separated. In the context of impurity physics, this model on a finite size chain allows for the creation of a single pair interacting with a fermionic bath or a single fermion interacting with a paired fermions bath.