Michael Groebner

Mag. Michael Gröbner, PhD


Technikerstrasse 25/4

A-6020 Innsbruck, Austria, Europe

Tel: +43 512 507 - 52426 (Office) or - 52532 (Lab)

Fax: +43 512 507 - 52499


Michael Gröbner was born on 21th April 1988 in Innsbruck, Austria. After receiving Matura, he attended the military service and started to study physics at the University of Innsbruck. In 2013, he finished his Master thesis under the supervision of Prof. H.-C. Nägerl and joined as a PhD student in the newly founded PoCeMoN (Ultracold Potassium - Cesium Molecules) team. Based on the results of his master thesis he developed a new quantum gas apparatus that allows for the first time the study of ultracold mixtures of bosonic/fermionic potassium and cesium. The research was focused on the simultaneous creation of degenerate samples of 39K and 133Cs, the observation of interspecies Feshbach resonances to obtain precise knowledge of the scattering properties and the improvement of cooling techniques that resulted in the coldest K samples after laser cooling. During this time, he was also involved in teaching classes for the physics program of the University of Innsbruck. In 2017, he received his PhD and at the same time finished his secondary teacher education (Lehramtsstudium) in physics and mathematics. Subsequently, he decided to stay as a post-doctoral fellow within the research group of Prof. H.-C. Nägerl and to extend his doctoral work. Michael's research interests are now primarily based on the creation of heteronuclear molecules and the observation of exotic quantum phases in non-trivial lattice geometries.


2017 - present

Postdoc at the PoCeMoN (Ultracold Potassium - Cesium Molecules) and the CsIII (A second generation Cs Bose-Einstein condensation experiment) experiment in the group of Prof. H.-C. Nägerl

2013 - 2017

PhD student at the PoCeMoN (Ultracold Potassium - Cesium Molecules) experiment in the group of Prof. H.-C. Nägerl. Thesis topic: Development of a new quantum gas apparatus for ultracold mixtures of K and Cs

2011 - 2013

Master Thesis in the group of R. Grimm under supervision of Prof. H.-C. Nägerl: "Aufbau und Charakterisierung eines Lasersystems zum Kühlen und Fangen von Kaliumatomen" at the CsIII experiment

2007 - 2013

Study of physics at the Leopold-Franzens-Universität Innsbruck

2010 - 2017

Secondary teacher education (Lehramtsstudium) in physics and mathematics at the Leopold-Franzens-Universität Innsbruck. Diploma thesis: "Bose-Einstein-Kondensation im Schulunterricht"


PoCeMoN - Ultracold Potassium - Cesium Molecules (H.-C. Nägerl)
CsIII - A second generation Cs Bose-Einstein condensation experiment (H.-C. Nägerl)


Research Highlights


Observation of interspecies Feshbach resonances in an ultracold 39K-133Cs mixture and refinement of interaction potentials

M. Gröbner, P. Weinmann, E. Kirilov, H.-C. Nägerl, P. S. Julienne, C. R. Le Sueur, and J. M. Hutson

We observe interspecies Feshbach resonances due to s-wave bound states in ultracold 39K-133Cs scattering for three different spin mixtures. The resonances are observed as joint atom loss and heating of the K sample. We perform least-squares fits to obtain improved K-Cs interaction potentials that reproduce the observed resonances, and carry out coupled-channel calculations to characterize the scattering and bound-state properties for 39K-Cs, 40K-Cs and 41K-Cs. Our results open up the possibilities of tuning interactions in K-Cs atomic mixtures and of producing ultracold KCs molecules.

Phys. Rev. A 95, 022715 (2017), arXiv:1612.07196



Degenerate Raman sideband cooling of 39K

M. Gröbner, P. Weinmann, E. Kirilov, and H.-C. Nägerl

We report on a first realization of sub-Doppler laser cooling of 39K atoms using degenerate three-dimensional Raman sideband cooling. We take advantage of the well-resolved excited hyperfine states on the D1 optical transition to produce spin polarized samples with 1.4x108 atoms at temperatures of 1.8 μK. The phase-space densities are ≥10-4, which significantly improves the initial conditions for a subsequent evaporative cooling step. The presented cooling technique using the D1 line can be adapted to other atomic species and is applicable to high-resolution imaging schemes in far off-resonant optical lattices.

Phys. Rev. A 95, 033412 (2017), arXiv:1612.07196


Observation of many-body long-range tunneling after a quantum quench

F. Meinert, M. J. Mark, E. Kirilov, K. Lauber, P. Weinmann, M. Gröbner, A. J. Daley, and H.-C. Nägerl

Quantum tunneling is at the heart of many low-temperature phenomena. In strongly correlated lattice systems, tunneling is responsible for inducing effective interactions, and long-range tunneling substantially alters many-body properties in and out of equilibrium. We observe resonantly enhanced long-range quantum tunneling in one-dimensional Mott-insulating Hubbard chains that are suddenly quenched into a tilted configuration. Higher-order tunneling processes over up to five lattice sites are observed as resonances in the number of doubly occupied sites when the tilt per site is tuned to integer fractions of the Mott gap. This forms a basis for a controlled study of many-body dynamics driven by higher-order tunneling and demonstrates that when some degrees of freedom are frozen out, phenomena that are driven by small-amplitude tunneling terms can still be observed.

Science 344, 1259-1262 (2014), arXiv:1312.2758


Publications and theses

see publications of our research group