Flexible and inelastic dipolar impacts in chromium BECs

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Versatile and inelastic dipolar impacts in chromium BECs Laboratoire de Physique des Lasers Université Paris Nord Villetaneuse - France B. Laburthe-Tolra B. Pasquiou P. Pedri E. Maréchal O. Gorceix G. Bismut L. Vernac A. Crubellier (LAC-Orsay) Former PhD understudies and post-docs: Q. Beaufils, T. Zanon , R. Chicireanu, A. Pouderous Former individuals from the gathering: J. C. Keller, R. Barbé

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Chromium : S=3 Dipole-dipole associations Long range Anisotropic Non nearby anisotropic meanfield Static and element properties of BECs

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Inelastic dipolar impacts Anisotropic dipole-dipole connections Spin level of opportunity coupled to orbital level of flexibility - Dipolar unwinding - Spinor material science and polarization elements

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Outline 1 Elastic Collective excitations in a Cr BEC 2 Inelastic Control of dipolar unwinding in optical cross sections Spontaneous demagnetization elements in optical grids

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Modification of BEC development because of dipole-dipole communications TF profile Striction of BEC (non neighborhood impact) Parabolic ansatz is still a decent ansatz Eberlein, PRL 92 , 250401 (2004) Pfau,PRL 95 , 150406 (2005)

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Collective excitations of a dipolar BEC Due to the anisotropy of dipole-dipole collaborations, their consequences for the BEC rely on upon the relative introduction of the attractive field and the hub of the trap Parametric excitations: Repeat the analysis for two bearings of the attractive field (differential estimation)

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Trap geometry reliance of the deliberate recurrence move BEC dependably extends along B Sign of quadrupole move relies on upon trap geometry Shift of the quadrupole mode recurrence (%) Shift of the viewpoint proportion (%) Related to the trap anisotropy Eberlein, PRL 92 , 250401 (2004) Good concurrence with Thomas-Fermi forecasts Large affectability of the aggregate mode to trap geometry not at all like the striction of the BEC

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Outline 1 Elastic Collective excitations in a Cr BEC 2 Inelastic Control of dipolar unwinding in optical cross sections Spontaneous demagnetization flow in optical grids

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Angle between dipoles Dipolar unwinding 3 2 1 0 - 1 Angular energy protection - 2 - 3 - Two stations for dipolar unwinding in m=3 (no DR in m=-3): Rotate the BEC ? Unconstrained production of vortices ? (Einstein-de-Haas impact) Need of a greatly decent control of B near 0 Santos, PRL 96 , 190404 (2006) See likewise Ueda, PRL 96 , 080405 (2006)

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How to watch the Einstein-de Haas impact ? Thoughts to facilitate the attractive field control necessities Create a crevice in the framework: B now should be controlled around a limited non-zero esteem Go to firmly kept geometries (BEC in 2D optical grids) Energy to nucleate a « mini-vortex » in a cross section site (~120 kHz) A pick up of two requests of extent on the attractive field prerequisites !

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Dipolar unwinding in a Cr BEC 3 2 1 Rf clear 1 Rf clear 2 0 - 1 - 2 Produce BEC m=-3 - 3 BEC m=+3, differ time distinguish BEC m=-3 Fit of rot gives b Born estimate Pfau, Appl. Phys. B, 77 , 765 (2003) Determines dissipating lengths See likewise Shlyapnikov PRL 73 , 3247 (1994) Never saw up to now

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Reduction of dipolar unwinding in optical grids Load the BEC in a 1D or 2D Lattice (retro-reflected Verdi laser) Rf clear 1 Rf clear 2 Load optical cross section BEC m=+3, shift time Produce BEC m=-3 distinguish m=-3 Look at warming; conclude b One expects a lessening of dipolar unwinding, as a consequence of the decrease of the thickness of states in the cross section

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3D 2D Dipolar unwinding rate parameter 10 - 19 m 3 s - 1 1D Strong diminishment of dipolar unwinding when Almost total concealment beneath an edge at 1D

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Suppression of dipolar unwinding in 1D: the aftereffect of barrel shaped symmetry (precise energy preservation) q Dipolar unwinding rate (u.a.) Below edge, suppresion of DR is most proficient if : Lattice destinations are round and hollow - The attractive field is parallel to the 1D gasses 0.8 0.6 Dipolar unwinding rate (u.a.) 0.4 Above edge : ought to deliver vortices in every grid site (EdH impact) … in advance … (issue of burrowing) 0.2 q

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Outline 1 Elastic Collective excitations in a Cr BEC 2 Inelastic Control of dipolar unwinding in optical grids Spontaneous demagnetization progression in 1D gasses

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Spinor ground state at low attractive field S=3 7 Zeeman expresses; all caught four disseminating lengths, a 6 , a 4 , a 2 , a 0 A rich spinor graph at low attractive field Different quantum stages at generally « large » attractive fields (mG) because of altogether different scrambling lengths Santos and Pfau PRL 96 , 190404 (2006) Diener and Ho PRL. 96 , 190405 (2006) 3 2 1 0 - 1 - 1 - 2 - 2 - 3 - 3 Magnetization progression set by dipole-dipole collaborations

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At VERY low attractive fields, unconstrained depolarization of 1D quantum gasses Load optical grid fluctuate time Produce BEC m=-3 Rapidly bring down attractive field Stern Gerlach tests

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An extinguish through a stage move ? Part in m=-3 Magnetic field (kHz) 3 2 1 0 - 1 - 2 - 3

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Magnetization flow in an expanded meanfield « Critical » field relies on upon substance potential Fraction in m=-3 Magnetic field (kHz) Td Strong warming in cross section, inconsequential to depolarization, still unaccounted for … in progresss… Remains underneath Td Temperature ( m K) Time (ms)

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(some more?) open inquiries: Tensor light-move: 3 - 3 2 - 2 1 - 1 0 Effect of non zero temperature ? Impacts on elements, stage graph… Santos PRA 75 , 053606 (2007) In which timescale will we achieve the new stage ? The most effective method to portray dipolar unwinding ? Impacts of 1D ?

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Conclusion Collective excitations – great concurrence with hypothesis Dipolar unwinding in lessened measurements - towards Einstein-de-Haas Spontaneous demagnetization in a quantum gas – initial moves towards spinor ground state (BECs in solid rf fields) (rf-helped unwinding) (rf affiliation) (d-wave Feshbach reverberation) (MOT of 53 Cr) Production of a (somewhat) dipolar Fermi ocean Load into optical grids – superfluidity ? Points of view

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L. Vernac E. Maréchal J. C. Keller G. Bismut Paolo Pedri B. Laburthe B. Pasquiou Q. Beaufils O. Gorceix Have left: Q. Beaufils, J. C. Keller, T. Zanon, R. Barbé, A. Pouderous, R. Chicireanu Collaboration: Anne Crubellier (Laboratoire Aimé Cotton)

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Influence of the BEC molecule number In our examination, MDDI is very little bigger than quantum active vitality Simulations with Gaussian anzatz It takes three times more iotas for the recurrence move of the aggregate mode to come to the TF forecasts than for the striction of the BEC

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