Dissociation of Feshbach molecules via spin-orbit coupling in ultracold Fermi gases

We study the dissociation of Feshbach molecules in ultracold Fermi gases with spin-orbit (SO) coupling. Since SO coupling can induce a quantum transition between Feshbach molecules and the fully polarized Fermi gas, the Feshbach molecules can be dissociated by the SO coupling. We experimentally realize this type of dissociation in ultracold gases of ${}^{40}\text{K}$ atoms with SO coupling created by Raman beams and observe that the dissociation rate is highly nonmonotonic on both the positive and negative Raman-detuning sides. Our results show that the dissociation of Feshbach molecules can be controlled by different degrees of freedoms, i.e., the SO-coupling intensity or the momenta of the Raman beams, as well as the detuning of the Raman beams.

Figure 1

(a) Schematic diagram of SO coupling for ${}^{40}\text{K}$. (b) Time sequence of the homogeneous bias magnetic field, the Raman coupling, and the rf field. Here $B_0=202.2$ G is the Feshbach resonance point of atoms in $|F=9/2,m_F=-9/2\rangle$ and $|F=9/2,m_F=-7/2\rangle$. The time of flight is denoted by TOF.

Figure 2

Ratio $N_{\mathrm{rem}}/N_{\mathrm{tot}}$ between the number $N_{\mathrm{rem}}$ of remaining Feshbach molecules and half the number $N_{\mathrm{tot}}$ of all atoms. Here we illustrate (a), (c), (e), and (g) experimental and (b), (d), (f), and (h) theoretical results as functions of Raman detuning $\eta$: (a) and (b) without SO coupling (the two Raman beams propagating along the same direction); (c) and (d) with binding energy of the Feshbach molecule $|E_b|=3.59E_r$, ramping time $T=30$ ms, and different values of the final intensity $\Omega$ of Raman coupling; (e) and (f) with $|E_b|=3.59E_r,\Omega =1.30E_r$, and different $T$; and (g) and (h) with $\Omega =1.30E_r,T=30$ ms, and different $|E_b|$.

Figure 3

Energy spectra of eigenstates of $H_F$ with two-photon detuning (a) $\eta =0$, (b) $\eta >0$, and (c) $\eta <0$.