Matteo Zaccanti

INO - Istituto Nazionale di Ottica | INO
Florence

Micro-scale ferromagnetism and quantum emulsions in quenched atomic Fermi gases

In this talk, I will report on recent experiments on the out-of-equilibrium dynamics of a two-component Fermi gas of ultracold lithium atoms, following a coherent quench to strong repulsive interactions.

Time-resolved pump-probe spectroscopy and spin density noise-correlation measurements enable to monitor the evolution of the system under the concurrent action of the ferromagnetic and pairing instabilities. At short timescales and for critical interactions, ferromagnetic correlations are found to overcome the pairing ones, fostering the formation of spin-polarized micro-domains. At longer times, while pairing processes inhibit spin de-mixing over larger length-scales, the system develops into a novel metastable state: a long-lived quantum emulsion consisting of polarized atomic micro-domains surrounded by bound fermion pairs. The relaxation of this spatially inhomogeneous many-body phase onto the paired ground state is found to be essentially hindered compared to that of the homogeneous system. Prospects for long-lived repulsive Fermi mixtures with mass imbalance will be also described.