Green Alaina, Li Hui, Toh Jun Hui See, Tang Xinxin, McCormick Katherine C, Li Ming, Tiesinga Eite, Kotochigova Svetlana, Gupta Subhadeep
Department of Physics, University of Washington, Seattle, Washington 98195, USA.
Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA.
Phys Rev X. 2020;10(3). doi: 10.1103/PhysRevX.10.031037.
We report on the observation of magnetic Feshbach resonances in a Fermi-Fermi mixture of ultracold atoms with extreme mass imbalance and on their unique -wave dominated three-body recombination processes. Our system consists of open-shell alkali-metal Li and closed-shell Yb atoms, both spin polarized and held at various temperatures between 1 and 20 K. We confirm that Feshbach resonances in this system are solely the result of a weak separation-dependent hyperfine coupling between the electronic spin of Li and the nuclear spin of Yb. Our analysis also shows that three-body recombination rates are controlled by the identical fermion nature of the mixture, even in the presence of -wave collisions between the two species and with recombination rate coefficients outside the Wigner threshold regime at our lowest temperature. Specifically, a comparison of experimental and theoretical line shapes of the recombination process indicates that the characteristic asymmetric line shape as a function of applied magnetic field and a maximum recombination rate coefficient that is independent of temperature can only be explained by triatomic collisions with nonzero, -wave total orbital angular momentum. The resonances can be used to form ultracold doublet ground-state molecules and to simulate quantum superfluidity in mass-imbalanced mixtures.
我们报告了在具有极端质量失衡的超冷原子费米-费米混合物中对磁费什巴赫共振的观测，以及对其独特的以 s 波为主导的三体复合过程的观测。我们的系统由开壳层碱金属锂和闭壳层镱原子组成，两者均自旋极化，并保持在 1 至 20 K 的不同温度下。我们证实，该系统中的费什巴赫共振完全是锂的电子自旋与镱的核自旋之间微弱的与间距相关的超精细耦合的结果。我们的分析还表明，即使在两种物种之间存在 s 波碰撞且在我们最低温度下复合率系数处于维格纳阈值范围之外时，三体复合率也受混合物相同费米子性质的控制。具体而言，复合过程的实验和理论线形比较表明，作为外加磁场函数的特征不对称线形以及与温度无关的最大复合率系数，只能通过具有非零 s 波总轨道角动量的三原子碰撞来解释。这些共振可用于形成超冷双重态基态分子，并模拟质量失衡混合物中的量子超流性。
