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Collaborations: L. Santos (Hannover)

Quantum magnetism with a chromium BEC in a 3D lattice. de Paz (PhD), A. Sharma (post-doc), A. Chotia (post doc) J. Huckans (visitor), O. Gorceix , E. Maréchal, L. Vernac , P. Pedri, B. Laburthe-Tolra. Collaborations: L. Santos (Hannover)

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Collaborations: L. Santos (Hannover)

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  1. Quantum magnetism with a chromium BEC in a 3D lattice • de Paz (PhD), A. Sharma (post-doc), A. Chotia (post doc) • J. Huckans (visitor), O. Gorceix , E. Maréchal, • L. Vernac , P. Pedri,B. Laburthe-Tolra Collaborations: L. Santos (Hannover) Former members: R. Chicireanu, Q. Beaufils, B. Pasquiou, G. Bismut

  2. Quantum Magnetism with a chromium BEC in a 3D lattice Vdd = Jila experiment = Jila experiment long range interactions magnetic dipole moment S=3 real spin = beyond the next neighbor quantum regime, high filling factor direct spin-spin interaction T < 1 nK to reach ground state Vdd = 10-20 Hz Spin dynamics in an out of equilibrium system

  3. 2 1 Quantum Magnetism with a chromium BEC in a 3D lattice different spin dynamics induced by dipole-dipole interactions in a Cr BEC loaded in a 3D lattice measurement of the evolution of the Zeeman states populations 3 2 1 Mott state 0 -1 -2 -3

  4. 2 1 Quantum Magnetism with a chromium BEC in a 3D lattice different spin dynamics induced by dipole-dipole interactions in a Cr BEC loaded in a 3D lattice measurement of the evolution of the Zeeman states populations 3 2 1 Mott state 0 -1 -2 -3 spin exchange constant magnetization magnetization = the atoms stay in the lowest band intrasite (contact) + intersite (dipole-dipole) spin exchange

  5. 2 1 Quantum magnetism with a dipolar BEC: Villetaneuse experiment different spin dynamics induced by dipole-dipole interactions in a Cr BEC loaded in a 3D lattice measure of the evolution of the Zeeman states populations 3 2 1 Mott state 0 -1 -2 -3 magnetization = dipolar relaxation change of the magnetization spin orbit coupling - band excitations intrasite dipole interactions

  6. 2 1 Quantum magnetism with a dipolar BEC: Villetaneuse experiment different spin dynamics induced by dipole-dipole interactions in a Cr BEC loaded in a 3D lattice measure of the evolution of the Zeeman states populations 3 2 1 Mott state 0 -1 -2 -3 dipolar relaxation change of the magnetization constant magnetization spin exchange

  7. Dipolar relaxation in a 3D lattice - observation of resonances nx , ny , nz kHz (Larmor frequency) 1 mG = 2.8 kHz width of the resonances: tunnel effect + B field, lattice fluctuations

  8. Dipolar relaxation in a 3D lattice – study of the first resonance kHz Final Initial spin state pair orbital momentum

  9. 2 1 Dipolar relaxation in a 3D lattice – effect of onsite contact interactions Atomic Fraction in m=+3 theory including intrasite contact interactions B (kHz) good agreement between theory for two atoms per site and experiment both for the shape and position of the resonance probe of the Mott distribution de Paz et al, Phys Rev A 87 (2013)

  10. Spin exchange dynamics in a 3D lattice 10 mG B 0 first resonance dipolar relaxation suppressed evolution at constant magnetization spin exchange from -2 experimental sequence: -1 -2 Load optical lattice -3 state preparation in -2 vary time Stern Gerlach analysis

  11. Different Spin exchange dynamics in a 3D lattice Contact interaction (intrasite) expected Mott distribution

  12. Different Spin exchange dynamics in a 3D lattice Contact interaction (intrasite) Dipole-dipole interaction (intersite) without spin changing term dipolar relaxation with doublons removed = only singlons expected Mott distribution

  13. Spin exchange dynamics in a 3D lattice: with only singlons the spin populations change! E(ms) = q mS2 comparison with a plaquette model (Pedri, Santos) 3*3 sites , 8 sites containing one atom + 1 hole quadratic light shift and tunneling taken into account measured with interferometry Proof of intersite dipolar coupling Many Body system

  14. Spin exchange dynamics in a 3D lattice with doublons at short time scale initial spin state onsite contact interaction: spin oscillations with the expected period strong damping contact spin exchange in 3D lattice: Bloch PRL 2005, Sengstock Nature Physics 2012

  15. Spin exchange dynamics in a 3D lattice with doublons at longer time scale intersite dipolar coupling result of a two site model: two sites with two atoms dipolar rate raised (quadratic sum of all couplings) our experiment allows the study of molecular Cr2 magnets with larger magnetic moments than Cr atoms, without the use of a Feshbach resonance not fast enough: the system is many body

  16. Spin exchange dynamics in a 3D lattice with doublons: strong reduction by a magnetic gradient if the spin dynamics results from intersite coupling it should disappear when: dipolar coupling rate amplitude Proof of intersite coupling

  17. Different Spin exchange dynamics with a dipolar quantum gas in a 3D lattice -1 -2 -3 intrasite contact intersite dipolar expected Mott distribution Heisenberg like hamiltonian quantum magnetism with S=3 bosons and true dipole-dipole interactions doublons removed = only singlons intersite dipolar de Paz et al, Arxiv (2013)

  18. thank you for your attention!

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