Contact parameters in two dimensions for general three-body systems

TL;DR

This paper investigates the three-body problem in two dimensions with distinguishable particles, deriving relations for wave functions and contact parameters, and analyzing how universality emerges in specific cases relevant to current experiments.

Contribution

It provides analytic relations for Faddeev components and explores the non-universality of contact parameters in general three-body systems in 2D.

Findings

Two-body contact parameter is not universal in general cases.

Universality is recovered when a subsystem has two identical non-interacting particles.

Three-body contact parameter is negligible when one subsystem is non-interacting.

Abstract

We study the two dimensional three-body problem in the general case of three distinguishable particles interacting through zero-range potentials. The Faddeev decomposition is used to write the momentum-space wave function. We show that the large-momentum asymptotic spectator function has the same functional form as derived previously for three identical particles. We derive analytic relations between the three different Faddeev components for three distinguishable particles. We investigate the one-body momentum distributions both analytically and numerically and analyze the tail of the distributions to obtain two- and three-body contact parameters. We specialize from the general cases to examples of two identical, interacting or non-interacting, particles. We find that the two-body contact parameter is not a universal constant in the general case and show that the universality is recovered when a subsystem is composed of two identical non-interacting particles. We also show that the three-body contact parameter is negligible in the case of one non-interacting subsystem compared to the situation where all subsystem are bound. As example, we present results for mixtures of Lithium with two Cesium or two Potassium atoms, which are systems of current experimental interest.