Group seminar at MPQ and Zoom: Spin-motion dynamics with ultracold polar molecules
 

Calder Miller from JILA, University of Colorado Boulder, USA
Group seminar at MPQ lecture hall and Zoom
Tuesday, 9 September, 09:00am (MEZ)

Optically trapped ultracold polar molecules offer a rapidly maturing platform for quantum science. Due to their strong, long-range, and tunable dipolar interactions, these systems are particularly suitable for realizing spin-motion models with rich many-body physics. Using a spin encoded in rotational states of fermionic KRb molecules, we demonstrated tuning of Heisenberg XXZ models with electric fields [1] and Floquet engineering of XYZ models with microwave pulse sequences [2]. By additionally regulating motion with optical lattices, we realized highly tunable generalized t-J models [3]. We used Ramsey spectroscopy to explore the out-of-equilibrium dynamics of these systems, observing one-axis and two-axis twisting at short times, and dephasing due to dipolar interactions and their coupling to motion at longer times. In addition to controlling interactions, observing new dynamics and phases predicted for these models requires preparing low-entropy initial states. Building on our previous work on selection of molecules in individual layers of an optical lattice [4] and electric field-assisted evaporative cooling [5,6], we report recent progress towards producing a deeply degenerate Fermi gas in an isolated 2D layer, enabling control of the anisotropy of the dipolar interactions. Using a tunable-spacing optical lattice, we compress a K-Rb mixture into a quasi-2D geometry. In this trap, we are able to produce ~20,000 ground state molecules at temperatures below the Fermi temperature. Through additional evaporative cooling, we aim to cool the system into deep degeneracy.

[1] J.-R. Li et al., Nature 614, 70-74 (2023).
[2] C. Miller et al., Nature 633, 332-337 (2024).
[3] A. N. Carroll et al., Science 388, 381-386 (2025). 
[4] W. G. Tobias et al., Science 375, 1299-1303 (2022). 
[5] G. Valtolina et al., Nature 588, 239-243 (2020).
[6] J.-R. Li et al., Nat. Phys. 17, 1144-1148 (201).