1 / 26

Ulrich Schneider

Fermions in optical lattices. Ulrich Schneider. Johannes Gutenberg-Universität Mainz. Ludwig-Maximilians Universität München. www.quantum.physik.uni-mainz.de/bec/. Ultracold Fermions. fermionic 40 K N=150-250 x 10 3 at T/T F <0.15. Crossed Dipole Trap 1030 nm (elliptical beams).

zenia
Download Presentation

Ulrich Schneider

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fermions in optical lattices Ulrich Schneider Johannes Gutenberg-Universität Mainz Ludwig-Maximilians Universität München www.quantum.physik.uni-mainz.de/bec/

  2. Ultracold Fermions • fermionic 40K • N=150-250 x 103 • at T/TF<0.15 Crossed Dipole Trap 1030 nm (elliptical beams) 50/50 spin mixture:

  3. Optical lattices dipole potential: blue detuned red detuned attractive repulsive Overlapping two counterpropagating laser beams produce a standing wave:

  4. independent control: • lattice depth • external confinement Dipole trap + blue lattice New feature in our apparatus: blue detuned lattice Dipole trap Blue lattice combined potential

  5. Fermi Hubbard Hamiltonian Tunneling Interaction Trap Control Knobs: • U/12J: scattering length (Feshbach resonance) • Et/12J:trap frequency

  6. Observables? • Momentum distribution: Fermions Bosons • Noise correlations: • In-situ cloud size compressibility • Doublon fraction

  7. Repulsive Interaction

  8. Band Insulator: 2 atoms per site Mott Insulator: 1 atom per site Metal: compressible Density distribution in trap T/TF=0.07 Theory: DMFT byT. A. Costi, R. W. Helmes, D. Rasch, and A. Rosch see also: L. De Leo et.al. PRL 101, 210403 (2008)

  9. Density distribution in trap T/TF=0.15

  10. Minimum in compressibility clear signature of Mott Insulator Metal Band Insulator Mott Plateau Theory: DMFT Cloud Size / Compressibility Theory: DMFT T. A. Costi et.al. see also: L. De Leo et.al. PRL 101, 210403 (2008)

  11. U. Schneider et.al. Science 322, 1520 Experimental results: Cloud Size

  12. U. Schneider et.al. Science 322, 1520 Experimental Results: Compressibility Observed minimum in compressibility is genuine signature of Mott Insulator

  13. U. Schneider et.al. Science 322, 1520 Experimental results: Pair Fraction U/12J=0 strong supression of doubly occupied sites U/12J=1/2 U/12J=1 strong correlated states see also: R. Jördens et.al. Nature 455, 204 (2008)

  14. T/TF = 0.15 S/N > 2 ln 2 Inhomogeneous entropy distribution Entropy of non-interacting gas in harmonic trap Entropy of Mott Insulator: S/N = ln 2 Trap is crucial!

  15. Temperature in lattice T/TF = 0.15

  16. Attractive Interaction

  17. L. Hackermüller et.al. in preparation Attractive Interactions Counterintuitive behavior: Cloud size grows for stronger attraction

  18. Attractive Interactions

  19. Dynamics

  20. Free Expansion band insulator

  21. Free Expansion in lattice: Sequence

  22. Bose-Fermi Mixtures

  23. Th. Best et.al. PRL 102, 030408 (2009) Bose-Fermi mixtures • Role of interactions in 87Rb-40K Bose-Fermi mixtures in a 3d optical lattice 3 Er 5 Er 9 Er 12 Er

  24. The future Many body physics of Fermions: • dynamic properties of fermionic Hubbard model • anti-ferromagnetic order • superfluid states?? • …

  25. Summary • Ultracold fermions in optical lattices are a • model system for solid state physics • Fermionic Mott Insulator • - minimum in compresibility • is genuine Mott feature • Attractive Interactions • entropy determines cloud size • Expansion • -crossover from ballistic to diffusive expansion

  26. People Experiments: U.S. Lucia Hackermüller Philipp Ronzheimer Thorsten Best Sebastian Will Simon Braun Kin Chung Fong Immanuel Bloch Johannes Gutenberg University Mainz Now: LMU/MPQ Munich Attractive IA: M. Moreno-Cardoner B. Paredes Johannes Gutenberg University Mainz T. Kitagawa E. Demler Harvard University E. Altmann Weizmann Institute DMFT: T.A. Costi R.W. Helmes D. Rasch A. Rosch University of Cologne Forschungszentrum Jülich

More Related