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Register a new userTwo-body relaxation of spin-polarized fermions in reduced dimensionalities near a p-wave Feshbach resonance
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We study inelastic two-body relaxation in a spin-polarized ultracold Fermi gas in the presence of a p-wave Feshbach resonance. It is shown that in reduced dimensionalities, especially in the quasi-one-dimensional case, the enhancement of the inelastic rate constant on approach to the resonance is strongly suppressed compared to three dimensions. This may open promising paths for obtaining novel many-body states.
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We report evidence for spin-rotation coupling in $p$-wave Feshbach resonances in an ultracold mixture of fermionic $^6$Li and bosonic $^{133}$Cs lifting the commonly observed degeneracy of states with equal absolute value of orbital-angular-momentum projection on the external magnetic field. By employing magnetic field dependent atom-loss spectroscopy we find triplet structures in $p$-wave resonances. Comparison with coupled-channel calculations, including contributions from both spin-spin and spin-rotation interactions, yields a spin-rotation coupling parameter $|gamma|=0.566(50)times10^{-3}$. Our findings highlight the potential of Feshbach resonances in revealing subtle molecular couplings and providing precise information on electronic and nuclear wavefunctions, especially at short internuclear distance. The existence of a non-negligible spin-rotation splitting may have consequences for future classifications of $p$-wave superfluid phases in spin-polarized fermions.
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.
We report on the experimental observation of a strongly interacting gas of ultracold two-electron fermions with orbital degree of freedom and magnetically tunable interactions. This realization has been enabled by the demonstration of a novel kind of Feshbach resonance occurring in the scattering of two 173Yb atoms in different nuclear and electronic states. The strongly interacting regime at resonance is evidenced by the observation of anisotropic hydrodynamic expansion of the two-orbital Fermi gas. These results pave the way towards the realization of new quantum states of matter with strongly correlated fermions with orbital degree of freedom.
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).
The narrow s-wave Feshbach resonance of a $^6$Li Fermi gas shows strong three-body loss, which is proposed to be used to measure the minute change of a magnetic field around the resonance. However, the eddy current will cause ultracold atom experiencing a magnetic field delayed to the desired magnetic field from the current of the magnetic coils. The elimination of the eddy current effect will play a key role in any experiments that motivated to measure the magnetic field to the precision of a part per million stability. Here, we apply a method to correct the eddy current effect for precision measurement of the magnetic field. We first record the three-body loss influenced by the effect of induced eddy current, then use a certain model to obtain the time constant of the actual magnetic field by fitting the atom loss. This precisely determines the actual magnetic field according to the time response of the three-body loss. After that, we implement the desired magnetic field to the atoms so that we can analyze the three-body loss across the whole narrow Feshbach resonance. The results show that the three-body recombination is the dominated loss mechanism near the resonance. We expect this practical method of correcting the eddy current error of the magnetic field can be further applied to the future studies of quantum few- and many-body physics near a narrow Feshbach resonance.
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