High spin at low temperatures
Dr. Christoph Becker (Institut für Laserphysik - Universität Hamburg)

A fundamental question in many-body physics is how collective behavior of many microscopically interacting particles gives rise to macroscopic properties such as superconductivity, giant magnetoresistance, or superfluidity.
Ultracold quantum gases are ideal candidates to address these questions because they offer excellent control over many crucial experimental parameters, such as the interaction strength, the dimensionality of the system and also the spin of the individual particles.
In my talk I will present a detailed survey of the physics of quantum degenerate Fermions with a large internal spin of F=9/2.
Starting with an experimental introduction to spin changing dynamics on the two-particle level I will present how a macroscopically large Fermi sea can behave as a single entity in spin space undergoing coherent collective oscillations in the spin degree of freedom.
I will discuss the influence of finite temperature as well as higher order collisional processes which counteract the systems tendency to evolve coherently and can lead to the occurrence of meta-stabel spin configurations.
Furthermore large spin quantum gases can be utilized to explore new aspects of the relaxation dynamics of a many-body system far from equilibrium.
We have performed measurements that reveal several collisional processes occurring on distinct time scales and moreover show that by tuning the magnetic field the character of an initial subset of spin states can be tuned from an open to a closed system.