Quantum Physics
Relaxation Dynamics of an Isolated Large-Spin Fermi Gas Far from Equilibrium
16 April 2014
Photo: AG Sengstock
We show that the spatial “collisions” of the atoms can flip their internal spins and lead to the relaxation of the spin-state distribution to its equilibrium. In our experiment, we knock an ultracold gas of potassium atoms out of its equilibrium by putting the atoms in two of the ten available internal spin states only. We then monitor how the atoms redistribute themselves among all ten states, and we are able to keep track of that process for time spans of up to 10 seconds by “counting” the number of atoms in each spin state. We have unraveled many aspects of the relaxation process: There are a number of different processes of atomic collision taking place at different time scales that cause spin changes, but the collision-aided spin-redistribution process is the slowest one in the whole system. Our results significantly advance the understanding of relaxation processes in quantum many-body systems and have been awarded as research highlight in Nature Physics.