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Bose-Einstein condensation of chromium

Bose-Einstein condensation of chromium. Ashok Mohapatra NISER, Bhubaneswar. SFB/TRR21. SFB/TRR 21. The team. Cr BEC team. Jonas. Axel. Tilman. Yong Wan (diploma student). Stefan. Ashok. Chromium. BEC, 2004 by Pfau’s group. Chromium.

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Bose-Einstein condensation of chromium

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  1. Bose-Einstein condensation of chromium Ashok Mohapatra NISER, Bhubaneswar

  2. SFB/TRR21 SFB/TRR 21 The team Cr BEC team Jonas Axel Tilman Yong Wan (diploma student) Stefan Ashok

  3. Chromium BEC, 2004 by Pfau’s group

  4. Chromium Large magnetic moment 6μB 36 times more dipolar interaction compared to alkali atoms

  5. 7P4 7P3 Repumper 663 nm MOT 425 nm 5D4 Optical Pumping 427 nm 7S3 Relevant energy levels of chromium Ti:Sa851 nm 2 W doubled (LBO) (600 mW)

  6. Experimental set up

  7. Steps to get the BEC Step 1: CLIP load Step 2: RF evapolarion to 15 μK and load to a dipole trap Step 3: Switch off the MT and optically pump the atoms to the energetically lowest Zeeman state to prevent the dipolar relaxation (large μB helps to flip the atoms to wrong Zeeman states)

  8. Steps to get the BEC Step 4: Forced evaporation in a crossed dipole trap A. Griesmaier, Phys. Rev. Lett. 94, 160401 (2005) Condensate of 50,000 atoms

  9. Feshbach resonances in Chromium J. Werner et al., Phys. Rev. Lett. 94, 183201 (2005) Braodest resonance @ 590 G, Δ~ 1.4 G Control of magnetic field to 10-5 is needed to have a noise of ±1a0 at 0 scattering length Active stabilization of the current in the Feshbach coils was used

  10. Feshbach resonances in Chromium B0 ~ 590 G ΔB ~ 1.4 G

  11. Broad feshabch resonance Fit: B0~ 590 G ΔB ~ 1.4 G

  12. Strong dipolar effects T. Lahaye, T. Koch, B. Fröhlich, M. Fattori, J. Metz, A. Griesmaier, S. Giovanazzi, T. Pfau; Nature 448, 672 (2007)

  13. Roton like excitation spectrum in a dipolar quantum gas L. Santos et al., PRL 90 250403 (2003) D-W. Wang et al., arXiv:0812.1838

  14. Dipolar coupling in classical ferrofluids Rosensweig instability M. D. Cowley and R. E. Rosensweig, J. Fluid Mech. 30, 671 (1967)

  15. Roton like excitation spectrum in classical ferrofluid Dispersion relation of surface wave in ferrofluid J. Browaeys et al., Braz. J. Phys. 31, 447 (2001) R. E. Rosensweig, Ferrohydrodynamics, Dover Publications, Inc (1997), page 191

  16. Roton like excitation spectrum in classical ferrofluid Spontaneous static deformation around critical magnetic field J. Browaeys et al., Braz. J. Phys. 31, 447 (2001) The rotonization mechanism in quantum dipolar gas a quantum could be a classical phenomenon………… Do we really need a superfluidity to have roton in quantum dipolar gas?????

  17. Roton and Supersolid phase in Rydberg dressed BEC Henkel et al., Phys. Rev. Lett. 104, 195302 (2010)

  18. Collective interaction using coherent Rydberg dressed BEC Honer et al, PRL 105, 160404 (2010)

  19. Thank you

  20. Rosensweig instability in classical ferrofluid Competition between the magnetic interaction with Gravity and surface free energy C. Gollwitzer et al.,, J. Fluid Mech. (2006) Surface wave Similar pattern in a quantum gas would lead to a supersolid state

  21. dipolar interaction in a BEC Field in y-direction Field in Z-direction J. Stuhler et al., Phys. Rev. Lett. 95 , 150406 (2005)

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