Just to throw something wild into this discussion, I make a post regarding temperatures below absolute zero that referred to dark energy.
The postulate made in it is very interesting. Anything that gets to a certain extreme temperature behaves as it's below absolute zero.
Just a clip from my post, which includes a video about temperatures below absolute zero.
https://similarworlds.com/physics/4969222-physics-TL-DR-A-temperature-below-absolute-zero
The achievement of the Munich physicists could additionally be interesting for cosmology, since the thermodynamic behaviour of negative temperature exhibits parallels to so-called dark energy. Cosmologists postulate dark energy as the elusive force that accelerates the expansion of the universe, although the cosmos should in fact contract because of the gravitational attraction between all masses. There is a similar phenomenon in the atomic cloud in the Munich laboratory:
