Ultracold fermion mixtures with tunable interactions:
polarons and the quest for novel superfluids

Rudolf Grimm

Univ. of Innsbruck and IQOQI, Austrian Academy of Sciences


Abstract:
The possibility to tune interatomic interactions by means of magnetically controlled Feshbach resonances has opened up unprecedented opportunities for experiments concerning the intriguing many-body physics of ultracold matter in the strongly interacting regime. After a brief general introduction, I will report on two main research lines pursued in our laboratories based on fermionic quantum mixtures with tunable interactions.


(1) A Fermi sea of Li-6 atoms is doped with impurity atoms of fermionic K-40 or bosonic K-41 atoms, which under strong interactions form quasiparticles. We explore the various properties of these “Fermi polarons” by means of radio-frequency spectroscopy. In our most recent experiments [1], we have observed mediated interactions between the polarons, with the surprising finding that the sign of the interaction depends on the quantum statistics of the impurity atoms.

(2) In a Fermi-Fermi mixture of Dy-161 and K-40, we are proceeding towards the creation of novel imbalanced fermion superfluids. After exploring the complex spectrum of Feshbach resonances, we have studied the spectrum of collective modes in the deep hydrodynamic regime and we have demonstrated the magneto-association of ultracold bosonic molecules under conditions near quantum degeneracy [2].

[1]   C. Baroni, I. Fritsche, E. Dobler, G. Anich, E. Kirilov, R. Grimm, M. A. Bastarrachea-Magnani,
P. Massignan, G. Bruun, Nat. Phys. (2023).


[2]   E. Soave, A. Canali, Z.-X. Ye, M. Kreyer, E. Kirilov, R. Grimm, Phys. Rev. Research 5, 033117 (2023).

 

Short biography:
1986 Diploma, Univ. of Hannover, Germany
1989 PhD, ETH Zurich, Switzerland
1989 – 1990: Postdoc at the Inst. of Spectroscopy, Troitsk, USSR
1990 – 2000: Researcher at the MPI for Nuclear Physics, Heidelberg, Germany
2000 – now: Professor of Experimental Physics, Innsbruck, Austria
2003 – now: Scientific Director at IQOQI Innsbruck, Austria

 
Major Awards / Honors:
2005 Wittgenstein Award (Austrian Science Fund and Federal Ministry)
2006 Elected Full Member of the Austrian Acad. of Sciences
2008 Science Prize of the State of Tyrol
2018 Faddeev Medal
2021 ERC Advanced Grant
2022 Toptica BEC Senior Award

 

More detailed information:
http://ultracold.at/grimm/rudi/