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Register a new userHighly Polarized Fermi Gases across a Narrow Feshbach Resonance
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We address the phase of a highly polarized Fermi gas across a narrow Feshbach resonance starting from the problem of a single down spin fermion immersed in a Fermi sea of up spins. Both polaron and pairing states are considered using the variational wave function approach, and we find that the polaron to pairing transition will take place at the BCS side of the resonance, strongly in contrast to a wide resonance where the transition is located at the BEC side. For pairing phase, we find out the critical strength of repulsive interaction between pairs above which the mixture of pairs and fermions will not phase separate. Therefore, nearby a narrow resonance, it is quite likely that magnetism can coexist with s-wave BCS superfluidity at large Zeeman field, which is a remarkable property absent in conventional BCS superconductors (or fermion pair superfluids).
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In this letter we show that the recently theoretically predicted and experimentally observed orbital Feshbach resonance in alkali-earth-like Yb-173 atom is a narrow resonance in energy, while it is hundreds Gauss wide in term of magnetic field strength, taking the advantage that the magnetic moment difference between the open and closed channels is quite small. Therefore this is an ideal platform for the experimental realization of a strongly interacting Fermi superfluid with narrow resonance. We show that the transition temperature for the Fermi superfluid in this system, especially at the BCS side of the resonance, is even higher than that in a wide resonance, which is also due to the narrow character of this resonance. Our results will encourage experimental efforts to realize Fermi superfluid in the alkali-earth-like Yb-173 system, the properties of which will be complementary to extensively studied Fermi superfluids nearby a wide resonance in alkali K-40 and Li-6 systems.
Three-body recombination is a phenomenon common in atomic and molecular collisions, producing heating in the system. However, we find the cooling effect of the three-body recombination of a 6Li Fermi gas near its s-wave narrow Feshbach resonance. Such counter-intuitive behavior is explained as follows, the threshold energy of the quasi-bounded Feshbach molecule acts as the knife of cooling, expelling the scattering atoms with selected kinetic energy from the trap. When the threshold energy happens to be larger than 3/2kBT, each lost atom in the three-body recombination process has more than 3kBT energy which results in cooling. The best cooling is found with the threshold energy set at about 3kBT, consistent with a theoretical model. The three-body recombination induced cooling raises potential applications for cooling complex atomic systems.
In this paper we explore the spin-orbit-induced bound state and molecular signature of the degenerate Fermi gas in a narrow Feshbach resonance based on a generalized two-channel model. Without the atom-atom interactions, only one bound state can be found even if spin-orbit coupling exists. Moreover, the corresponding bound-state energy depends strongly on the strength of spin-orbit coupling, but is influenced slightly by its type. In addition, we find that when increasing the strength of spin-orbit coupling, the critical point at which the molecular fraction vanishes shifts from zero to the negative detuning. In the weak spin-orbit coupling, this shifting is proportional to the square of its strength. Finally, we also show that the molecular fraction can be well controlled by spin-orbit coupling.
Ultracold gases of interacting spin-orbit coupled fermions are predicted to display exotic phenomena such as topological superfluidity and its associated Majorana fermions. Here, we experimentally demonstrate a route to strongly-interacting single-component atomic Fermi gases by combining an s-wave Feshbach resonance (giving strong interactions) and spin-orbit coupling (creating an effective p-wave channel). We identify the Feshbach resonance by its associated atomic loss feature and show that, in agreement with our single-channel scattering model, this feature is preserved and shifted as a function of the spin-orbit coupling parameters.
We study three-atom inelastic scattering in ultracold textsuperscript{39}K near a Feshbach resonance of intermediate coupling strength. The non-universal character of such resonance leads to an abnormally large Efimov absolute length scale and a relatively small effective range $r_e$, allowing the features of the textsuperscript{39}K Efimov spectrum to be better isolated from the short-range physics. Meticulous characterization of and correction for finite temperature effects ensure high accuracy on the measurements of these features at large-magnitude scattering lengths. For a single Feshbach resonance, we unambiguously locate four distinct features in the Efimov structure. Three of these features form ratios that obey the Efimov universal scaling to within 10%, while the fourth feature, occurring at a value of scattering length closest to $r_e$, instead deviates from the universal value.
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