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Ultracold gases are ensembles of atoms held at a temperature near absolute zero. Such systems enable the creation of exotic phenomena such as Bose–Einstein condensation. Ultracold gases are also useful simulating condensed-matter systems because their tunability opens the door to effects that are otherwise difficult to observe.
Two adjacent layers flowing at different velocities in the same fluid are subject to flow instabilities. This phenomenon is now studied in atomic superfluids, revealing that quantized vortices act as both sources and probes of the unstable flow.
Evaporative cooling is the prevailing method for achieving ultracold temperatures in atomic systems, but the schemes to remove hotter atoms are limited by the spatial profile of the trapping potential. To overcome this limitation, the authors demonstrate a three-body recombination-based collisional cooling scheme for selective removal of hotter atoms.
Efimov states have very weak binding energy and show intriguing characteristics. Here the authors use high-resolution coherent spectroscopy to show the existence of an Efimov state embedded in the atom-dimer continuum for narrow Feshbach resonances in 7Li atoms.
This study describes experiments with ultracold lithium Fermi gases in which many-body pairing leads to the emergence of a pseudogap, and it confirms theoretical predictions relevant to cuprate superconductivity.
R.-J. Slager et al. extend the theory of multigap topology from static to non-equilibrium systems. They identify Floquet-induced non-Abelian braiding, resulting in a phase characterized by anomalous Euler class, a multi-gap topological invariant. They also find a gapped anomalous Dirac string phase. Both phases have no static counterparts and exhibit distinct boundary signatures.
Quantum simulators can provide new insights into the complicated dynamics of quantum many-body systems far from equilibrium. A recent experiment reveals that underlying symmetries dictate the nature of universal scaling dynamics.
Quasicrystals are ordered but not periodic, which makes them fascinating objects at the interface between order and disorder. Experiments with ultracold atoms zoom in on this interface by driving a quasicrystal and exploring its fractal properties.
Optical atomic clocks are extremely accurate sensors despite the poor use of their resources. A parallel quantum control approach might help to optimize the resources of optical atomic clocks, which could lead to an exponential improvement in their performance.
Landau’s theory of Fermi liquids predicts that impurities embedded in a Fermi sea of atoms form quasiparticles called polarons that interact with one another via the surrounding medium. Such mediated polaron–polaron interactions have been directly observed and are shown to depend on the quantum statistics of the impurities.
A new binding mechanism between trapped laser-cooled ions and atoms has been observed. This advancement offers a novel control knob over chemical reactions and inelastic processes on the single particle limit.