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arXiv:2302.14253 · Journal of the Physical Society of Japan

Observation of Feshbach Resonances in an167Er–6Li Fermi–Fermi Mixture

F. Schäfer, Yuki Haruna, Yoshiro Takahashi

Published Apr 19, 2023• 15 citations
arXivHTMLPDF

Abstract

We present our experimental investigation of the interspecies Feshbach spectrum in a mixture of ${}^{167}$Er($F = 19/2, m_F = -19/2$)-${}^6$Li($F = 1/2, m_F = 1/2$) atoms in the microkelvin temperature regime. These temperatures are achieved by means of sympathetic cooling with ${}^{174}$Yb as a third species. Interspecies Feshbach resonances are then identified by investigation of the Er-Li inelastic collisional properties for magnetic fields up to 800 G. Numerous narrow resonances as well as six resonances with widths above 1 G could be identified. It is these broader resonances that hold much promise for interesting future investigations of, for exmample, novel superfluid states and Efimov states in large mass-imbalanced, all-fermionic two-component systems.

DOI
10.7566/jpsj.92.054301

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We present our experimental investigation of the interspecies Feshbach spectrum in a mixture of 167{}^{167}167Er(F=19/2,mF=−19/2F = 19/2, m_F = -19/2F=19/2,mF​=−19/2)-6{}^66Li(F=1/2,mF=1/2F = 1/2, m_F = 1/2F=1/2,mF​=1/2) atoms in the microkelvin temperature regime. These temperatures are achieved by means of sympathetic cooling with 174{}^{174}174Yb as a third species. Interspecies Feshbach resonances are then identified by investigation of the Er-Li inelastic collisional properties for magnetic fields up to 800 G. Numerous narrow resonances as well as six resonances with widths above 1 G could be identified. It is these broader resonances that hold much promise for interesting future investigations of, for exmample, novel superfluid states and Efimov states in large mass-imbalanced, all-fermionic two-component systems.
We report on the experimental observation of Feshbach resonances in large-mass-imbalance mixtures of erbium (Er) and lithium (Li). All combinations of 168Er,166Er^{168}\mathrm{Er}, ^{166}\mathrm{Er}168Er,166Er, and 7Li,6Li^{7}\mathrm{Li}, ^{6}\mathrm{Li}7Li,6Li are cooled to temperatures of a few microkelvin, partially by means of sympathetic cooling together with ytterbium (Yb) as a third mixture component. The Er-Li inelastic interspecies collisional properties are studied for magnetic fields up to 680G680\phantom{\rule{0.28em}{0ex}}\mathrm{G}680G. In all cases, resonant interspecies loss features, indicative of Feshbach resonances, have been observed. While most resonances have sub-Gauss widths, a few of them are broad and feature widths of several Gauss. Those broad resonances are a key to the realization of ultracold Er-Li quantum gas mixtures with tunable interactions.
This thesis reports on the tunability of interactions in ultracold Bose-Fermi mixtures of Cesium and Lithium. The \nfirst realization of an optically trapped \n6Li -133Cs mixture enabled to perform trap loss spectroscopy measurements to identify \nmagnetic Feshbach resonances. A total of 19 interspecies Feshbach resonances, all in the magnetic field range between 650 G and 950 G, were observed for the two energetically lowest spin states of each species. Two 5 G broad and especially two 60 G broad s-wave resonances give perspectives to produce a dipolar quantum gas of LiCs ground state molecules as well as to study the Efimov effect in highly mass imbalanced systems. In addition, a unique relative tunability of intra- and interspecies \nscattering lengths was found which makes the 6Li -133Cs system also well suited for the investigation of polarons. Evaporative cooling was performed on optically trapped samples which contained only one of the species. In this way, Bose-Einstein condensates of 6Li molecules as well as 133Cs samples at a phase-space density of p = 4 · 10^2 were prepared. All experiments were performed in a new apparatus, which has been designed and set up during this thesis.
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Magnetic Feshbach resonances in 7Li−133Cs^{7}\text{Li}-^{133}\text{Cs}7Li−133Cs mixtures
Motivated by the prospect of observing Efimov and Bose polaron physics in ultracold mixtures of bosonic atoms with large mass imbalance, this work investigates the magnetic Feshbach resonances between 7Li^{7}\text{Li}7Li and 133Cs^{133}\text{Cs}133Cs. The resonances are predicted at the 1 gauss level using the model of Pires et al. [Phys. Rev. A, 90, 012710] obtained from experimental observations of resonances between 6Li^{6}\text{Li}6Li and 133Cs^{133}\text{Cs}133Cs. It is found that a few resonances in a practical range of magnetic field intensity could be used to tune the scattering length between 7Li^{7}\text{Li}7Li and 133Cs^{133}\text{Cs}133Cs atoms. Opportunities for observing Efimov and Bose polaron physics are discussed.