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Demagnetization cooling of a gas


Adiabatic demagnetization is an efficient technique for cooling solid samples by several orders of magnitude in a single cooling step. In gases, the required coupling between dipolar moments and motion is typically too weak, but in dipolar gases—of high-spin atoms or heteronuclear molecules with strong electric dipole moments, for example—the method should be applicable. Here, we demonstrate demagnetization cooling of a gas of ultracold 52Cr atoms. Demagnetization is driven by inelastic dipolar collisions, which couple the motional degrees of freedom to the spin degree. In this way, kinetic energy is converted into magnetic work, with a consequent temperature reduction of the gas. Optical pumping is used to magnetize the system and drive continuous demagnetization cooling. We can increase the phase-space density of our sample by up to one order of magnitude, with almost no atom loss, suggesting that the method could be used to achieve quantum degeneracy via optical means.

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Figure 1: Illustration of demagnetization cooling.
Figure 2: Single-step demagnetization.
Figure 3: Continuous demagnetization cooling.


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We thank our atom optics group for encouragement and practical help. We thank G. J. Beirne for careful reading of the manuscript. This work was supported by the German Science Foundation (DFG) (SPP1116 and SFB/TR 21).

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Authors and Affiliations



M.F., T.K. and S.G. carried out the experimental work and data analysis, A.G. carried out experimental work and S.H., J.S. and T.P. were responsible for project planning.

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Correspondence to M. Fattori or T. Pfau.

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The authors declare no competing financial interests.

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Fattori, M., Koch, T., Goetz, S. et al. Demagnetization cooling of a gas. Nature Phys 2, 765–768 (2006).

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