Emergence of a pseudogap in ultracold gases

The most recent publication by Associate Prof. Joaquin Drut, in collaboration with Aurel Bulgac and Adam Richie-Halford from the University of Washington, appeared today in Physical Review Letters. In this work, Drut and colleagues investigate strongly correlated Fermi systems with pairing interactions, which become superfluid below a critical temperature Tc. While superfluidity and superconductivity of weakly coupled systems is well understood, many open questions remain for cases where interactions are strong. For example, the extent to which pairing correlations alter the behavior of the liquid at temperatures T>Tc is a subtle issue that remains hotly debated. This applies, in particular, to the appearance of the so-called pseudogap in the BCS-BEC crossover of unpolarized spin-1/2 nonrelativistic matter. To shed light on this strongly correlated fluid, Drut and colleagues used non-perturbative computational techniques to extract several universal quantities that characterize that system. They conclude that there is no clear evidence that the pseudogap vanishes at the unitary point (the universal point in the middle of the crossover) and draw a similarity between the issue of the emergence of the pseudogap and the precise location of the edge of the atmosphere (the Karman line).