Gregarious bosonic atoms can act like antisocial fermionic atoms, theorists predict, and the fake-fermions can form pairs that mimic a long-sought new state of matter.
Cooling atoms, both bosons and fermions, to ultra-low temperatures has provided the opportunity to probe distinct quantum phases of matter. The ability to then trap these atoms, or even molecules, in optical lattices and tune the interactions between them presents the possibility of an ideal and clean quantum system that can act as a surrogate for complex condensed-matter systems in which the tuning parameters may be limited. To date, most boson-boson and boson-fermion mixtures in this context have been formed with atoms of the same element. Forming more complex molecules with multiple elements offers the prospect of adding an anisotropic electric dipole interaction into the mix, thereby opening up a number of applications in quantum information processing and metrology. Voigt et al. demonstrate the formation and trapping of ultracold diatomic heteronuclear molecules using 6Li and 40K fermionic atoms. Forming long-lived bosonic molecules from two fermionic species with such different masses offers a rich parameter space in which to study many-body correlated systems with asymmetric interactions. — ISO
Inhomogeneous superfluidity lies at the heart of many intriguing phenomena in quantum physics. It is believed to play a central role in unconventional organic or heavy-fermion superconductors, chiral quark matter, and neutron star glitches. However, so far even the simplest form of inhomogeneous superfluidity, the Fulde-Ferrell (FF) pairing state with a single center-of-mass momentum, is not conclusively observed due to the intrinsic complexibility of any realistic Fermi systems in nature. Here we theoretically predict that the controlled setting of ultracold fermionic atoms with synthetic spin-orbit coupling induced by a two-photon Raman process, demonstrated recently in cold-atom laboratories, provides a promising route to realize the long-sought FF superfluidity. At experimentally accessible low temperatures, the FF superfluid state dominates the phase diagram, in sharp contrast to the conventional case without spin-orbit coupling. We show that the finite center-of-mass momentum carried by Cooper pairs is directly measurable via momentum-resolved radio-frequency spectroscopy. Our work opens the way to direct observation and characterization of inhomogeneous superfluidity.
We first show a possible way to create a new type of matter, free-neutron Bose-Einstein condensate by the ultracold free-neutron-pair Bose-Einstein condensation and then determine the neutron drip line experimentally. The Bose-Einstein condensation of bosonic and fermionic atoms in atomic gases was performed experimentally and predicted theoretically early. Neutrons are similar to fermionic atoms. We found free neutrons could be cooled to ultracold neutrons with very low energy by other colder neutral atoms which are cooled by the laser. These neutrons form neutron pairs with spin zero, and then ultracold neutron-pairs form Bose-Einstein condensate. Our results demonstrate how these condensates can react with accelerated ion beams at different energy to synthesize very neutron-rich nuclides near, on or/and beyond the neutron drip line, to determine the neutron drip line and whether there are long-life nuclide or isomer islands beyond the neutron drip line experimentally. Otherwise, these experimental results will confirm our prediction that is in the whole interacting region or distance of nuclear force in all energy region from zero to infinite, Only repulsive nuclear force exists among identical nucleons and only among different nucleons exists attractive nuclear force.