Mimicking Magnets

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Science  23 Dec 2011:
Vol. 334, Issue 6063, pp. 1607
DOI: 10.1126/science.334.6063.1607-a

When a solid with electrons confined to two dimensions is placed in a magnetic field at low temperature, its transverse electrical conductivity may become quantized; this collective phenomenon is known as the quantum Hall effect (QHE). Because solid-state systems in which QHE occurs are limited by their material properties, it is desirable to simulate the effect in a more tunable and less disordered context, such as a cold atomic gas placed in an optical lattice. However, neutral atoms are not affected by a magnetic field the way electrons are. Experimenters previously found a way around that issue by creating an effective magnetic field analogue through rotating the gas, or applying Raman lasers, but the interesting strong field regime had not been reached. Now, Aidelsburger et al. have placed an ultracold gas in a two-dimensional optical lattice where the potential was staggered in one direction, leading to suppressed tunneling. Tunneling was recovered through coupling to a pair of Raman lasers, but as a consequence, the tunneling atoms' wave functions acquired a phase equivalent to the presence of a strong magnetic field. The strength of the field could be tuned by changing the angle between the lasers, and its presence was confirmed through the cyclotron-like orbits of the atoms.

Phys. Rev. Lett. 107, 255301 (2011).

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