Luttinger liquid of trimers in Fermi gases with unequal masses

TL;DR

This paper explores the formation and properties of trimer states in one-dimensional attractive Fermi gases with unequal masses, revealing a novel trimer Luttinger liquid phase with suppressed superfluidity.

Contribution

It demonstrates the existence of trimer bound states in mass-imbalanced Fermi gases and characterizes a new trimer Luttinger liquid phase at specific densities.

Findings

Existence of three-body bound states (trimers) with different tunneling rates.

Identification of a trimer Luttinger liquid phase with an energy gap.

Calculation of binding energy and effective mass of trimers.

Abstract

We investigate one dimensional attractive Fermi gases in spin-dependent optical lattices. We show that three-body bound states - "trimers" - exist as soon as the two tunneling rates are different. We calculate the binding energy and the effective mass of a single trimer. We then show numerically that for finite and commensurate densities $n_\uparrow=n_\downarrow/2$ an energy gap appears, implying that the gas is a one-component Luttinger liquid of trimers with suppressed superfluid ordering. The boundaries of this novel phase are given. We discuss experimental situations to test our predictions.