Speaker
Description
We investigate quantum atom-ion scattering in the s-wave regime using a
hybrid apparatus comprising a single $^{138}$Ba$^{+}$ ion in a linear Paul trap and a $^{6}$Li Fermi gas. The atomic sample is prepared via sequential cooling in a magneto-optical trap (MOT) and a compressed MOT (cMOT) before confinement in a crossed optical dipole trap (xODT). Inelastic collision rates are manipulated via magnetically tunable Feshbach resonances. To overcome micromotion-induced energy limits in RF traps, we use radial displacement fields $E_{dc}$ to control the ion’s excess kinetic energy $\Delta E_{\text{ion}}$. This technique, calibrated via molecular dynamics (MD) simulations, allows for the systematic tuning of collision energies over four orders of magnitude—from the classical $E^{−3/4}$ scaling regime to below the s-wave limit $E_{s} = 8.8$ µK · $k_{B}$.
We present a characterization of the Feshbach spectrum between 240 G and
340 G with an average resonance density of 0.58(1) G$^{−1}$, utilizing fluorescence-based detection of ion survival probability $P_{\text{surv}}$. Technical emphasis is placed on the manipulation of the substructure of individual three-body resonances. We demonstrate that the resonance position, width, and amplitude are modulated by the external fields and the ion’s driven motion. These techniques enable high-speed interaction control, a prerequisite for future many-body quantum
simulations.
| Academic level | PhD student |
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