Universal tetramer and pentamer in two-dimensional fermionic mixtures

TL;DR

This paper investigates universal four- and five-body bound states in two-dimensional fermionic mixtures, identifying critical mass ratios and analyzing their properties, with implications for cold atom experiments and many-body physics.

Contribution

It introduces the existence of universal tetramer and pentamer states in 2D fermionic mixtures and determines the critical mass ratios for their formation.

Findings

Critical mass ratio for tetramer: 3.38

Critical mass ratio for pentamer: 5.14

Distinct density and momentum correlations for tetramers and pentamers

Abstract

We study the emergence of universal tetramer and pentamer bound states in the two-dimensional $(N+1)$ system, which consists of $N$ identical heavy fermions interacting with a light atom. We show that the critical heavy-light mass ratio to support a ($3+1$) tetramer below the trimer threshold is $3.38$, and to support a ($4+1$) pentamer below the tetramer threshold is $5.14$. While these ground state tetramer and pentamer are both with zero total angular momentum, they exhibit very different density distributions and correlations in momentum space, due to their distinct angular momentum decompositions in the dimer-fermion frame. These universal bound states can be accessible by a number of Fermi-Fermi mixtures now realized in cold atoms laboratories, which also suggest novel few-body correlations dominant in their corresponding many-body systems.