Lithium Quantum Gas Microscope

Lithium Quantum Gas Microscope

Probing strong correlations physics in the Fermi Hubbard model.

Ultracold atoms in optical lattices have proven to be a powerful tool to study quantum many-body systems. Recent experiments have demonstrated the potential of single-site resolved detection in optical lattices for the study of strongly correlated bosonic systems. In our experiment we plan to apply similar techniques to fermions. We use spin mixtures of Lithium-6 atoms to produce a degenerate fermionic many-body system trapped in an 3D optical lattice with a lattice spacing of about 1.2 μm.

With a high resolution imaging system, we are be able to resolve single sites in a 2D plane of the lattice and image single atoms. In our experiments, we aim at exploring the quantum phases of the Fermi-Hubbard Hamiltonian while making use of the novel detection tools of quantum gas microscopy.

Imaging a single magnetic polaron. Using quantum gas micrscopy, we are able to directly image distortions in the antiferromagentic background around mobile impurities in the Fermi Hubbard model.

Experimental setup

We heat a block (approx. 2x2cm) of the fermionic Lithium-6 isotope to 350 degree centigrade in an oven, generating an atomic beam out of a small aperture. A standard decreasing-field Zeeman slower decelerates the atoms, which are then captured and cooled in a Magneto-Optical Trap (MOT) operating at 671nm in a steel octagon chamber. At this stage we end up with 109 atoms at a temperature of about 300 μK. Next, a second MOT is switched on operating at the narrow 2S1/2 ↔ 3P3/2 transition at 323nm. After this UV cooling stage we end up with ~5*108 atoms at roughly 70 μK. The UV light is provided by a home build laser system using two nonlinear frequency conversions. The UV MOT also enables the direct loading of an optical dipole trap at a magic wavelength close to 1070nm, where the relative light-shift of the transition vanishes. Using a large volume high power dipole trap we capture a 10 million cold atoms from the UV MOT. A second, more tightly focused dipole trap at 1064nm is switched on afterwards, to transport the atoms from the MOT chamber into the main glass cell. This is achieved by mechanically moving the focus of the 1064nm beam. At the final position, the transport trap is crossed with another trapping beam to increase the density and allow for efficient evaporative cooling to degeneracy in a Feshbach field.

Optical Lattice Generation

After the final evaporation the degenerate sample of atoms is loaded to the optical lattice. The lattice is produced via an interferometric projection method. A modified Michelson interferometer generates pairs of phase coherent, parallel beams which are sent through the high resolution objective (NA=0.5, ~1 μm resolution at 670nm). The objective transforms the spatial offset from the optical axis of the incoming beams into an angle under which the beams intersect at the focal position. Four pairs of beams (each pair is phase coherent) are sent through the objective such that we obtain two 2D optical lattices. We choose the beam separation such that a 2D superlattice is generated at the position of the atoms. Using a similar interferometer setup, we project another set of beams from the side to generate a superlattice along the vertical direction.

Selected Recent Publications

Koepsell, J. M.S.; Vijayan, J.; Sompet, P.; Grusdt, F.; Hilker, T. A.; Demler, E. A.; Salomon, G.; Bloch, I.; Groß, C.: Imaging magnetic polarons in the doped Fermi-Hubbard model. Nature 572 (7769), pp. 358 - 362 (2019)
Salomon, G.; Koepsell, J. M.S.; Vijayan, J.; Hilker, T. A.; Nespolo, J.; Pollet, L.; Bloch, I.; Groß, C.: Direct observation of incommensurate magnetism in Hubbard chains. Nature 565 (7737), pp. 56 - 60 (2019)
Hilker, T. A.; Salomon, G.; Grusdt, F.; Omran, A.; Boll, M.; Demler, E. A.; Bloch, I.; Groß, C.: Revealing hidden antiferromagnetic correlations in doped Hubbard chains via string correlators. Science 357 (6350), pp. 484 - 488 (2017)
Boll, M.; Hilker, T. A.; Salomon, G.; Omran, A.; Nespolo, J.; Pollet, L.; Bloch, I.; Groß, C.: Spin- and density-resolved microscopy of antiferromagnetic correlations in Fermi-Hubbard chains. Science 353 (6305), pp. 1257 - 1260 (2016)
Omran, A.; Boll, M.; Hilker, T. A.; Kleinlein, K.; Salomon, G.; Bloch, I.; Groß, C.: Microscopic Observation of Pauli Blocking in Degenerate Fermionic Lattice Gases. Physical Review Letters 115 (26), 263001 (2015)

Research Group Members

Bloch, Immanuel Prof. Dr.
  • +49 89 3 29 05 - 238 (MPQ)
Bojovic, Petar
Master Student
  • +49 89 3 29 05 - 631 (Office) // -275 (Lab) //
  • -225 (Prep lab)
Bourgund, Dominik
Doctoral candidate
  • +49 89 3 29 05 - 713 (Office) // -275 (Lab) //
  • -225 (Office) // -275 (Lab) // (Prep lab)
Groß, Christian Dr.
Research Group Leader
  • +49 89 3 29 05 - 713 (Office)
Hirthe, Sarah
Doctoral candidate
  • +49 89 3 29 05 - 626 (Office) // -275 (Lab) //
  • -225 (Prep lab)
Koepsell, Joannis M.Sc.
Doctoral candidate
  • +49 89 3 29 05 - 713 (Office) // -275 (Lab) //
  • -225 (Prep lab)
Sompet, Pimonpan Dr.
  • +49 89 3 29 05 - 713 (Office) // -275 (Lab) //
  • -225 (Prep lab)

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