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Physicists Produce "Left-Handed" Composite MaterialsPhysicists supported by the National Science Foundation (NSF) have produced a new class of composite materials with physical properties that scientists theorized might be possible, but had never before been produced. The materials are called "left-handed" because they reverse many of the physical properties observed in ordinary materials in response to electromagnetic radiation. Lead scientists Sheldon Schultz and David Smith of the University of California at San Diego will announce their findings today at a meeting of the American Physical Society in Minneapolis, Minn. and publish them in a future issue of Physical Review Letters. The new class of materials has the ability to reverse properties such as the Doppler effect, the principle that changes the frequency of waves as the source of the waves moves. Thus, a train whistle sounds higher in pitch as the train approaches and lower as the train recedes. Maxwell's equations, which describe the relationship between magnetic and electric fields, suggest that microwave radiation or light would show the opposite effect in this new class of materials, shifting to lower frequencies as the source approaches. Similarly, Maxwell's equations suggest that a lens made of such materials, instead of dispersing electromagnetic radiation as usual, would focus it as it passes through. "If these effects turn out to be possible at optical frequencies, this material would have the crazy property that a flashlight shining on a slab can focus the light at a point on the other side," said Schultz. The scientists demonstrated the ability to reverse these properties by beaming microwave radiation through a composite material produced from a series of thin copper rings and ordinary copper wire strung parallel to the rings. Their results verified the composite had negative electric permittivity and negative magnetic permeability. In most known materials in nature, these qualities are positive. The composite created by the team is among a new class of materials called "metamaterials," in which the way two or more materials are mixed, or arranged, at a very fine level can affect the electromagnetic properties of the resulting composite. Ultimately, the development of this new class of left-handed metamaterials, which was financed by NSF and the Department of Energy, could have applications in areas such as microwave transmissions, antennae design, and optical components.
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