Fermi liquid to Bose condensate crossover in a two-dimensional ultracold gas experiment
By controlling interparticle interactions it is possible to transform a fermionic system into a bosonic system and vice versa while preserving quantum degeneracy. Evidence of such a transformation may be found by monitoring the pressure and interference. The Fermi pressure is an indication of the fermionic character of a system, while the interference implies a nonzero order parameter and Bose condensation. Changing from three to two spatial dimensions introduces new physics and makes the system more difficult to describe due to the increased fluctuations and the reduced applicability of mean-field methods. An experiment with a two-dimensional ultracold atomic gas shows a crossover between the Bose and Fermi limits, as evident from the value of pressure and from the interference pattern, and provides data to test models of 2D Fermi and Bose systems, including the most-difficult-to-model strongly coupled systems.