Observation of dipolar splittings in high-resolution atom-loss spectroscopy of ${}^6\mathrm{Li}$ $p$-wave Feshbach resonances

We report on the observation of dipolar splitting in ${}^6\mathrm{Li}p$-wave Feshbach resonances by high-resolution atom-loss spectroscopy. The Feshbach resonances at 159, 185, and $215\mathrm{G}$ exhibit a doublet structure of 10, 6, and $13\mathrm{mG}$, respectively, associated with different projections of the orbital angular momentum. The observed splittings agree well with coupled-channel calculations. We map out the temperature dependence of the atom-loss spectrum and extrapolate resonance positions as well as the corresponding widths to zero temperature. The observed dipolar splitting in fermionic lithium might be useful for the realization of the quantum phase transition between the polar and axial $p$-wave superfluid phases.

Figure 1

${}^6\mathrm{Li}p$-wave FRs in the $|1\rangle \oplus |1\rangle$, $|1\rangle \oplus |2\rangle$, and $|2\rangle \oplus |2\rangle$ entrance channels observed as atomic-loss features. The figure shows the fractional remaining Li atoms in spin-state $|1\rangle$ (solid squares) or $|2\rangle$ (open circles) after a holding time of 500, 150, and 100 ms from left to right, respectively. All three resonances show doublet structures, where quantum numbers $m_l$ are assigned according to theoretical modeling. The data of spin-state $|2\rangle$ for the resonance near $185\mathrm{G}$ is vertically shifted to avoid overlapping with that of $|1\rangle$. The solid curves are fits of multipeak Gaussian functions from which the resonance positions $B^e$ (indicated by vertical dashed lines) and widths $w^e$ are extracted as listed in Table 1.

Figure 2

Temperature dependence of trap-loss spectrum near the $214\text{−}\mathrm{G}{}^6\mathrm{Li}p$-wave FR. (a) Loss spectrum at different sample temperatures. The baselines of the profiles are shifted according to $T$, as shown at the right axis. The data are fitted using a double-Gaussian function to extract the loss peak positions $B_{m_l}^e$ and widths $w_{|m_l|}^e$. The dotted vertical line shows the extrapolated peak position of $B_1^e$ at zero temperature at $214.824\mathrm{G}$. (b) $B_{|m_l|}^e$ (black symbols) and $w_{|m_l|}^e$ (red symbols) of the observed loss features at different $T$ for the $|m_l|=1$ (solid circles) and $m_l=0$ (open squares) components. $B_{|m_l|}^e$ are referenced to the zero-temperature value of $B_1^e$ at $214.824\mathrm{G}$. The lines are linear fits to the data.