Bound states in a quasi-two-dimensional Fermi gas

TL;DR

This paper investigates bound states of fermions and a distinguishable particle in a quasi-2D setting, revealing the existence of universal tetramers with potential experimental relevance.

Contribution

It introduces a model for N fermions plus one particle in quasi-2D, demonstrating the existence of universal non-Efimov tetramers at certain mass ratios and confinement strengths.

Findings

Non-Efimov trimers exist for M/m<13.6 in quasi-2D.

A bound tetramer can form for M/m as low as 5 under strong confinement.

The energy of the system can be approximated by an effective two-channel model.

Abstract

We consider the problem of N identical fermions of mass M and one distinguishable particle of mass m interacting via short-range interactions in a confined quasi-two-dimensional (quasi-2D) geometry. For N=2 and mass ratios M/m<13.6, we find non-Efimov trimers that smoothly evolve from 2D to 3D. In the limit of strong 2D confinement, we show that the energy of the N+1 system can be approximated by an effective two-channel model. We use this approximation to solve the 3+1 problem and we find that a bound tetramer can exist for mass ratios M/m as low as 5 for strong confinement, thus providing the first example of a universal, non-Efimov tetramer involving three identical fermions.