Comment on "Observation of Bose-Einstein Condensation of Molecules", cond-mat/0311617

TL;DR

This comment challenges the interpretation of a Bose-Einstein condensation experiment, proposing that the observed state may be a novel many-body state distinct from BCS or molecular BEC, based on energy considerations.

Contribution

It offers an alternative interpretation of experimental results, suggesting the existence of a new many-body state beyond traditional BCS or molecular BEC.

Findings

The experiment's low energy state may indicate a novel many-body phase.

The measured scattering amplitude does not necessarily imply a small true scattering amplitude.

The observed state could be fundamentally different from BCS or molecular BEC states.

Abstract

In this comment, we argue that the recent experiment of Ketterle and co-workers does not necessarily need to be interpreted as indicating that the true scattering amplitude between two molecules becomes small (8 nm measured vs. 120 nm predicted). Rather it can be interpreted as indicating that the energy of the achieved state is much lower than both the (variational) energy for a BCS state and the energy of a molecular condensate. In this sense, we suggest that the experiment may point to a novel many-body state, that is neither the BCS nor the molecular BEC state, and that still has to be identified.