Two-fluid coexistence in a spinless fermions chain with pair hopping

TL;DR

This paper demonstrates a novel coexistence phase in a one-dimensional spinless fermions model, where paired and unpaired fermions form separate Luttinger liquids, revealed through numerical and theoretical analysis.

Contribution

It introduces a new phase with coexistence of paired and unpaired fermions in a simple 1D model, supported by DMRG simulations and a two-fluid theoretical model.

Findings

Identification of a coexistence phase in the model

Numerical confirmation via DMRG calculations

Development of a two-fluid theoretical description

Abstract

We show that a simple one-dimensional model of spinless fermions with pair hopping displays a phase in which a Luttinger liquid of paired fermions coexists with a Luttinger liquid of unpaired fermions. Our results are based on extensive numerical density-matrix renormalisation group calculations and are supported by a two-fluid model that captures the essence of the coexistence region.