Two-body correlations in N-body boson systems

TL;DR

This paper develops a hyperspherical method to analyze two-body correlations in N-boson systems, revealing new multi-body Efimov states and showing correlations significantly lower interaction energy, with comparisons to mean-field and experimental results.

Contribution

It introduces a variational hyperspherical approach with a Faddeev-like decomposition to study correlations and Efimov states in N-boson systems, extending understanding beyond mean-field models.

Findings

Correlations lower interaction energy substantially.

Identification of new multi-body Efimov states.

Agreement with experimental data and mean-field results.

Abstract

We formulate a method to study two-body correlations in a system of N identical bosons interacting via central two-body potentials. We use the adiabatic hyperspherical approach and assume a Faddeev-like decomposition of the wave function. For a fixed hyperradius we derive variationally an optimal integro-differential equation for hyperangular eigenvalue and wave function. This equation reduces substantially by assuming the interaction range much smaller than the size of the N-body system. At most one-dimensional integrals then remain. We view a Bose-Einstein condensate pictorially as a structure in the landscape of the potential given as a function of the one-dimensional hyperradial coordinate. The quantum states of the condensate can be located in one of the two potential minima. We derive and discuss properties of the solutions and illustrate with numerical results. The correlations lower the interaction energy substantially. The new multi-body Efimov states are solutions independent of details of the two-body potential. We compare with mean-field results and available experimental data.