Speaker
Description
The presented ultracold gases experiment uses bosonic $^{133}$Cs and fermionic $^6$Li. Because of their large mass ratio also qualitatively new observation become accessible. An example is the universal scaling law of Efimov states which has been investigated [1,2]. Currently, we are aiming for the creation of a Fermi polaron. In the infinitely heavy impurity limit the Fermi polaron loses is quasiparticle nature, which is known as the Anderson orthogonality catastrophe [3]. Since the chosen species are close to this limit, some precursors of this effect are predicted to arise [4,5]. For higher mass imbalance also the molecule-polaron crossover shifts to strong interactions which enriches the observable effects in this mixture [6,7,8].
In our apparatus a stable creation of a single species Fermi gas with $T/T_F \approx 0.2$ has been realized. We also set up a scheme with a sequential loading of the two species, which includes the movement of the Cs sample in a large optical dipole trap out of the center, to separate the preparation of the two components. Spectroscopic probes have been built up for $^{133}$Cs (via a zero momentum Raman transition) as well as for $^6$Li (using a radio frequency antenna). The combination of both spectroscopy methods allows for a direct distinction between molecules and polarons [9].
We will present the current status of the project at the time of the conference, which is expected to include a precise characterization of the sequential loading scheme as well as first spectroscopy signals of a degenerate gas with impurities.
Short bio (50 words) or link to website
- B. Sc. (2018) and M.Sc. (2021) in physics: Karlsruhe (Germany);
Bachelor and Master thesis: optical fiber-based micro resonators for quantum networking (Prof. David Hunger) - since 2021: PhD student in Heidelberg (Germany). Ultracold mixture experiment with Lithium and Cesium to explore polaron physics (Prof. Matthias Weidemüller/Prof. Lauriane Chomaz)
References
[1] Pires, R.; Ulmanis, J.; Häfner, S.; Repp, M.; Arias, A.; Kuhnle, E. D.; Weidemüller, M. Observation of Efimov Resonances in a Mixture with Extreme Mass Imbalance. Phys. Rev. Lett. 2014, 112 (25), 250404.
[2] Ulmanis, J.; Häfner, S.; Pires, R.; Kuhnle, E. D.; Wang, Y.; Greene, C. H.; Weidemüller, M. Heteronuclear Efimov Scenario with Positive Intraspecies Scattering Length. Phys. Rev. Lett. 2016, 117 (15), 153201.
[3] Anderson, P. W. Infrared Catastrophe in Fermi Gases with Local Scattering Potentials. Phys. Rev. Lett. 1967, 18 (24), 1049–1051.
[4] Schmidt, R.; Knap, M.; Ivanov, D. A.; You, J.-S.; Cetina, M.; Demler, E. Universal Many-Body Response of Heavy Impurities Coupled to a Fermi Sea: A Review of Recent Progress. Rep. Prog. Phys. 2018, 81 (2), 024401.
[5] Adlong, H. S.; Liu, W. E.; Turner, L. D.; Parish, M. M.; Levinsen, J. Signatures of the Orthogonality Catastrophe in a Coherently Driven Impurity. Phys. Rev. A 2021, 104 (4), 043309.
[6] Massignan, P. Polarons and Dressed Molecules near Narrow Feshbach Resonances. EPL 2012, 98 (1), 10012.
[7] Trefzger, C.; Castin, Y. Impurity in a Fermi Sea on a Narrow Feshbach Resonance: A Variational Study of the Polaronic and Dimeronic Branches. Phys. Rev. A 2012, 85 (5), 053612.
[8] Parish, M. M.; Adlong, H. S.; Liu, W. E.; Levinsen, J. Thermodynamic Signatures of the Polaron-Molecule Transition in a Fermi Gas. Phys. Rev. A 2021, 103 (2), 023312.
[9] Schirotzek, A.; Wu, C.-H.; Sommer, A.; Zwierlein, M. W. Observation of Fermi Polarons in a Tunable Fermi Liquid of Ultracold Atoms. Phys. Rev. Lett. 2009, 102 (23), 230402.
| Career stage | Student |
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