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arXiv:2505.22409 · Physical Review Letters

Precision Measurement of Spin-Dependent Dipolar Splitting in Li 6 p -Wave Feshbach Resonances

Shuai Peng, Sijia Peng, Lijun Ren, Shaokun Liu, Bin Liu, Jiaming Li, Le Luo

Published Sep 4, 2025• 3 citations
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Abstract

The magnetic dipolar splitting of a p-wave Feshbach resonance is governed by the spin-orbital configuration of the valence electrons in the triplet molecular state. We perform high-resolution trap-loss spectroscopy on ultracold ^{6}Li atoms to resolve this splitting with sub-milligauss precision. By comparing electron-spin-polarized (|m_{S}|=1) and electron-spin-mixture (m_{S}=0) configurations of the triplet state, we observe a clear spin-dependent reversal in the splitting structure, confirmed via momentum-resolved absorption imaging. This behavior directly reflects the interplay between electron spin projection m_{S} and orbital angular momentum m_{ℓ} in the molecular states. Our results provide a stringent benchmark for dipole-dipole interaction models and lay the groundwork for controlling the pairing in p-wave superfluid systems.

DOI
10.1103/5nns-xkt4

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Abstract We report precision, orbital-resolved measurements of three-body recombination near the 159 G p -wave Feshbach resonance in an ultracold gas of 6 Li atoms prepared in their lowest hyperfine state. Using a radio-frequency gated protocol that suppresses magnetic-field transients below the milligauss level, we resolve loss features associated with the | m ℓ | = 1 and m ℓ = 0 orbital projections. The measured three-body loss coefficient L 3 is well captured by a thermally averaged cascade-recombination model, enabling extraction of the resonance splitting δ B and effective-range parameter k e . At the lowest temperature, we obtain δ B = 7.6 ( 3 ) mG and k e = 0.151 ( 6 ) a 0 − 1 , both in quantitative agreement with coupled-channel theory. These results establish orbital-resolved three-body spectroscopy as a precision probe of p -wave scattering and provide a benchmark for microscopic models of resonant few-body loss.
We report the observation of a dimensional crossover of a ppp-wave Feshbach resonance in an ultracold, spin-polarized 6^66Li Fermi gas confined by a one-dimensional optical lattice. Using high-resolution atom-loss spectroscopy, we resolve the orbital doublet associated with the $\ml=0$ and $|\ml|=1$ scattering channels over a wide range of lattice depths. In the weak-confinement regime, the atom loss signal associated with the $|\ml|=1$ branch is stronger, consistent with the twofold orbital degeneracy of the three-dimensional system. As the lattice confinement increases, the relative loss weight of the two orbital branches evolves continuously toward the quasi-two-dimensional limit, indicating a progressive suppression of relative motion along the lattice direction. In addition, we observe a systematic confinement dependence of the orbital splitting between the two resonance branches. These results provide an experimental characterization of orbital-dependent ppp-wave scattering in reduced dimensions and motivate future microscopic studies of confined anisotropic scattering.