Physics

Confined, Cold, but Still Moving

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Science  14 Apr 2000:
Vol. 288, Issue 5464, pp. 229
DOI: 10.1126/science.288.5464.229e

The observation of metallic behavior in dilute two-dimensional electron gases (2DEG) that was first observed six years ago came as a surprise because the prevailing theory indicated that such systems should be insulating. Further experiments revealed that a metal-to-insulator transition (MIT) occurred as the electron density in the 2DEG was varied. Several theories have since been proposed to explain these intriguing results, but so far no consensus on a leading candidate has emerged.

Kravchenko and Klapwijk now introduce experimental results extending the lower temperature region over which the MIT can be observed. Of particular interest is the result for the electron density pegged exactly at the critical value. At that point, the resistivity remained temperature-independent all the way down to 35 millikelvin. Although a clear understanding of the mechanism driving the effect remains elusive, these new results do place constraints on possible theoretical models.—ISO

Phys. Rev. Lett.84, 2909 (2000).

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