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Universal spin dynamics in two-dimensional Fermi gases

Nature Physics volume 9, pages 405–409 (2013)Cite this article

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A Corrigendum to this article was published on 31 January 2014

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Abstract

Harnessing spins as information carriers has emerged as an elegant extension to the transport of electrical charges1. The coherence of such spin transport in spintronic circuits is determined by the lifetime of spin excitations and by spin diffusion. Fermionic quantum gases allow the study of spin transport from first principles because interactions can be precisely tailored and the dynamics is on directly observable timescales2,3,4,5,6,7,8,9,10,11,12. In particular, at unitarity, spin transport is dictated by diffusion and the spin diffusivity is expected to reach a universal, quantum-limited value on the order of the reduced Planck constant ħ divided by the mass m. Here, we study a two-dimensional Fermi gas after a quench into a metastable, transversely polarized state. Using the spin-echo technique13, for strong interactions, we measure the lowest transverse spin diffusion constant14,15 so far 6.3 (8) × 10-3 ħ/m. For weak interactions, we observe a collective transverse spin-wave mode that exhibits mode softening when approaching the strongly interacting regime.

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Figure 1: Quench of a 2D Fermi gas in which all atoms were initially prepared in the |↓〉 state.
Figure 2: Spin-echo signals in the strongly interacting regime.
Figure 3: Observation of spin waves for the non-interacting gas ().
Figure 4: Spin waves in the collisionless regime as a function of interaction strength.

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Change history

  • 04 June 2013

    In the version of this Letter originally published online, in the third main paragraph, the formula for the maximum elastic scattering cross section between atoms should have read σ∼λdBD−1. In the previous paragraph, penultimate sentence, the terms 'parallel to M' and 'orthogonal to M' should not have been included. In the section 'Interactions in two dimensions', the first equation should have included square brackets, as here: f(q) = 4π/[ln(1/q2a2D2)+iπ]. These corrections have been made in the HTML and PDF versions of the Letter.

  • 23 December 2013

    In the version of this Letter originally published, the stated value for the difference in the gyromagnetic ratio for the |↑> and |↓> state, δγ, was missing a factor of 2π. Consequently, the diffusion constants were overestimated by a factor of (2π)2. In particular, the value at ln(kFa2D) = 0 stated in the text should be 6.3(8) × 10-3ħ/m instead of 0.25(3)ħ/m. Other quantities, such as the magnetic field gradient, which was independently calibrated, are not affected. All other statements and observations in the published version are correct and remain unaffected. These errors have now been corrected in the online versions of the Letter.

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Acknowledgements

We thank E. Altman, G. Conduit, E. Demler, U. Ebling, A. Eckardt, C. Kollath, M. Lewenstein, A. Recati and W. Zwerger for discussions and B. Fröhlich and M. Feld for contributions to the experimental apparatus. The work has been supported by EPSRC (EP/J01494X/1, EP/K003615/1), the Leverhulme Trust (M. Koschorreck), the Royal Society, the Wolfson Foundation, and the Alexander-von-Humboldt Professorship.

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Authors and Affiliations

  1. Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK

    Marco Koschorreck, Daniel Pertot, Enrico Vogt & Michael Köhl

  2. Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany

    Michael Köhl

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  1. Marco Koschorreck
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  2. Daniel Pertot
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  3. Enrico Vogt
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Contributions

The measurements were conceived by M. Koschorreck and M. Köhl, data were taken by M. Koschorreck, D.P., and E.V., data analysis and writing of the manuscript was performed by M. Koschorreck and M. Köhl.

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Correspondence to Marco Koschorreck or Michael Köhl.

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The authors declare no competing financial interests.

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Koschorreck, M., Pertot, D., Vogt, E. et al. Universal spin dynamics in two-dimensional Fermi gases. Nature Phys 9, 405–409 (2013). https://doi.org/10.1038/nphys2637

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