Abstract
Quantum simulation with ultracold atoms has become a powerful technique to gain insight into interacting many-body systems. In particular, the possibility to study nonequilibrium dynamics offers a unique pathway to understand correlations and excitations in strongly interacting quantum matter. So far, coherent nonequilibrium dynamics has exclusively been observed in ultracold many-body systems of bosonic atoms. Here we report on the observation of coherent quench dynamics of fermionic atoms. A metallic state of ultracold spin-polarized fermions is prepared along with a Bose-Einstein condensate in a shallow three-dimensional optical lattice. After a quench that suppresses tunnelling between lattice sites for both the fermions and the bosons, we observe long-lived coherent oscillations in the fermionic momentum distribution, with a period that is determined solely by the Fermi-Bose interaction energy. Our results show that coherent quench dynamics can serve as a sensitive probe for correlations in delocalized fermionic quantum states and for quantum metrology.
Highlights
Quantum simulation with ultracold atoms has become a powerful technique to gain insight into interacting many-body systems
The investigation of nonequilibrium dynamics in interacting quantum many-body systems has emerged as a major research direction in the field of ultracold atoms
Nonequilibrium dynamics has been explored in transport measurements that allowed for a semi-classical theoretical description[18]
Summary
To illustrate the emergence of coherent quench dynamics, we consider an elementary setup with two lattice sites[23] (labeled 1 and 2, spaced by distance a), occupied by a single fermion and multiple bosons (see Fig. 1b). For n(k) to evolve with time, delocalized fermions and spatially varying bosonic occupancies are required In the experiment, the latter is provided by the quantum fluctuations of the on-site occupation that are characteristic for a BEC. The momentum profiles relax towards a state with a more uniform distribution across the Brillouin zone (Fig. 2c), as a consequence of equilibration due to residual tunnelling (see Methods). On increasing the attraction between fermions and bosons, the period of the oscillations becomes shorter as expected from the theoretical analysis This confirms that the quench dynamics is driven by the interspecies interaction UFBpaFB. Residual tunnelling after the quench is expected to induce damping and to reduce the oscillation amplitude[28,29]
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